Alex is a marine biologist, aquarist, lover of animals, an experienced veterinary assistant, and has a Bachelor of Science in Biology.

Where to Begin?

You have your perfect tank, complete with all the bells and whistles of filtration. You have your water quality test kit ready. You have a list of fish you would like in your collection. So, how are you going to decorate your aquarium? Believe it or not, this is where a lot of people run into problems. Sometimes they get so excited about all the cute decorations at the pet store that they overcrowd the bottom of the tank. This is no good. Not only will this make doing tank maintenance harder (just think of trying to gravel wash all that), but it also it looks tacky. With that in mind, how do you pick out decorations for your tank? This is the time to be creative, as the sky is truly the limit.

Work From the Bottom Up

What Aquarium Substrate Should You Use?

The first thing you want to consider is what kind of substrate to use. There are many different options. Do you want a sandy bottom? What about small gravel, or large? You can even use small stones. Do you want to use glass pebbles? Do you want the tank to be colorful or more natural?

The most important thing to consider when choosing a substrate is your fish. Sometimes the type of fish you want will dictate what kinds of substrate you have to use. If you want fish like eels or knifefish, you need to have a sandy bottom. Eels will spend most of their time on the bottom, and if you have a rocky substrate, they will rub their bodies raw, which is bad for them. If you are considering a freshwater ray, then you need to have a large bottom with sand. They will bury themselves in the sand, which would be nearly impossible for them to do safely in a tank with gravel as the substrate. Sand will also give your tank more of a saltwater feel, which many people desire.

However, sand does have some downsides. If you plan on doing gravel washes, which you should strongly consider, sand can make them more annoying. Since the sand is smaller and lighter than gravel, it tends to travel higher up the tube. It also tends to end up in whatever you are using to collect your waste water. This means that you will need to replace sand more often than you would have to replace gravel.

Gravel and stones are popular choices for freshwater tanks. They create a natural look for the tank and they are easy to clean. They are a better alternative to colored glass pebbles which, however pretty, are not always the best choice for a large fish tank. Glass pebbles aren't necessarily bad for your fish, they simply do not provide as much surface area for good bacteria to colonize. You need good bacteria to keep the nitrogen levels in your tank in check. Glass pebbles over time will break down, as is natural, and gravel will erode as well. However, the glass pebbles will have sharper edges whereas the gravel will just become finer. Glass pebbles are pretty, but they are just for show. It would not be harmful to have a few of them scattered throughout the bottom of the tank, as they will add some color. Just be sure to change them out once they begin to show signs of wearing down.

You need to make sure that everything you put into your tank is properly rinsed—and that includes your substrate. Sometimes you need to rinse it a few times to get all of the dust and debris out.

Plants: Live or Fake?

Choosing the Right Plants for Your Aquarium: Real or Fake?

Plants are a very popular decoration in many aquariums. Some people like them because they add color to the tank. Some add them because plants are found in many freshwater environments and can give the tank a more natural feel. If you go to the pet store, you will see a wide array of choices when it comes to aquarium plants.

The vast majority of home aquariums use plastic plants in place of live ones. Why? The plastic plants are often more colorful than real plants, coming in colors that are not found in in nature. They are also easier to maintain since they cannot die. And, like real plants, they offer the fish a place to hide.

However, real plants can offer systems something fake plants cannot: They can help improve the water quality of your tank. How is this? Plants need to use nitrogen and in an aquarium they are able to use the fishes' waste products. This keeps the levels low in the tank, which is a great bonus. Plants also use CO2 (carbon dioxide) for their respiration and give off O2 (oxygen) as a waste product. This is great for home tanks, as carbon dioxide build-up can be toxic and stable oxygen levels not only help your fish breathe, they can help maintain a stable pH level.

Of course, fake plants do have their own advantages: They don't drop leaves or die. Dead leaves and plants decompose, which can cause nitrogen levels in the tank to spike. This spike can stress the fish and, if it is high enough, could potentially lead to death.

Adding Decorations

Dos and Don'ts of Decorating a Fish Tank

The sky is truly the limit when it comes to adding decorations to fish tanks. You can even get a miniature replica of Bikini Bottom or Stonehenge if that is what you are into. Pet store shelves are lined with fake rocks, corals, and sunken ships, as well as many other oddities. These items have been specifically designed to be in fish tanks. This means that the materials used will not deteriorate when submerged in water for long periods of time.

There are a few things to keep in mind when picking out decorations for your tank. You need to know exactly how big the bottom of your tank is. You also need to keep in mind anything else you might already have. Are you adding plants? How many? The last thing you need to keep in mind is exactly what you want your tank to look like. Many people often go overboard when it comes to picking out decorations for their tank. It can be really easy to do, and let's face it, it's really fun to pick things out for your tank. Just keep in mind how much space you have to work with. Do you really have room for that sunken ship, fake corals, and the giant treasure chest? Sometimes simpler is better. One large piece and a couple of smaller pieces are all you need, especially if you are adding plants.

You might be tempted to add real coral and driftwood. This can be dangerous. You do not want to add any diseases or parasites to your tank. Also disturbing coral reefs is illegal in many places, not to mention extremely frowned upon in the aquarist and diver communities. Since I do not support this practice, I will not discuss it further. But, I will say this: Live coral loses its color once it dies, and wouldn't you rather have fake coral that has a realistic color instead of a white mass in your tank?

Sometimes people are tempted to add things that have not been designed to go in fish tanks. You would be surprised what some people want to use as decoration. Sharp edges, concrete, copper, and plastics that have been painted should not be put in your fish tank. Why? These items will cause problems. Copper is toxic to fish and concrete is going to leach chemicals into your tank. Sharp edges can harm your fish and should always be avoided. Paint can flake off or poison your fish. If you ever put something in your tank and notice that it seems to be flaking or the paint is disappearing, remove it immediately.

When in doubt, do not add it to your tank. It is better to be safe than sorry. After all, do you really want to endanger your fish just for the sake of having costume jewelry in your tank? Always keep in mind that no matter what you add, you want to rinse it thoroughly before it goes in.

Things That Don't Belong in Fish Tanks

• Ceramics (if you cannot eat off it, don't put it into your tank; they can leach chemicals and heavy metals)
• Wood (unless it was purchased at a pet store and has been pretreated)
• Rocks (some rocks have minerals that you do not want in your tank)
• Shells and corals (in freshwater systems, they will add calcium that the system does not need)
• Some glass (glass is safe unless it has sharp edges or has been painted)
• Plastics (general rule of thumb is if it smells like plastic, it doesn't go in a fish tank)

How to Clean Aquarium Decorations

No matter what you use for decorations, except for live plants, you are going to need to clean it at some point. You are going to need some basic tools to clean your tank and decorations. Scrub brushes with bristles, soft pad scrub pads, and a gravel wash kit are a few of the items that I would recommend. Be sure to get items that go with your tank, and keep in mind that acrylic scratches much more easily than glass, so never use a rough brush or pad on an acrylic tank.

1. Scrub Off Algae and Built-Up Gunk

The first thing you want to do is scrub off any algae or gunk from your decorations and the walls of the tank. The hard bristled brush is good for scrubbing the decorations and the soft pads, especially with the long handles, are good for the walls.

2. Change Out the Water

Once you have scrubbed the algae, it is time for the water change.

3. Clean the Substrate

Cleaning the substrate is easy, and you remove your water at the same time. Two birds with one stone, what is better than that? A gravel wash tube is typically an acrylic tube with a flexible hose that goes into a bucket. The acrylic tube and hose use suction to shake up the gravel and pull dirty water, detritus, and poop through the hose and into the bucket.

How often you should clean your gravel depends on several factors. How many fish do you have? Do you often overfeed your fish? Do you have live plants that lose leaves? Even if your tank has excellent water quality, you should consider doing small gravel washes weekly to remove the excess food, poop, and detritus.

Cleaning the decorations in your tank keeps them bright and the tank healthier. It is also very satisfying to see all the gunk that you remove from the gravel of your tank.

How to Gravel Wash

Methods Behind Gravel Washing

Should You Add a Tank Background?

Many hobbyists opt to have a background on their tank. There are many different options for backgrounds. They come in different colors and patterns. Really, there are no wrong choices, so you can do whatever your heart desires. If you want a plain blue background, go for it. If you want a sunken ship in your background, have at it. If you want a picture of the castle at Disneyland, knock yourself out.

If you don't want a background, you don't need to have one. Some people just don't like the look of the wall behind the back being visible from the front of the tank. It is really a matter of personal choice. Personally, it doesn't bother me to see the wall behind my tank, but when I do use backgrounds I make sure that I hide the tape well. I can't stand being able to see the tape; I feel it makes my beautiful tank look tacky.

On a side note: I have never seen the Disneyland castle as a background option at a pet store. But, if you happen to have a picture (and if you don't, the Internet is a lovely place), you can simple have a picture printed to the correct size and laminated. Why laminated? Think about it. At some point, no matter how careful you are, you are going to get water on the background.

Questions & Answers

Question: My wife likes to rearrange the layout of our aquarium every week. It seems to make one of our African Cichlids a little more aggressive. Is it ok for her to keep doing this, or should we leave the stuff alone?

Answer: Changing the layout of your aquarium is a good way of adding enrichment. I did it all the time when I worked at an aquarium. For some species of fish, a place to hide is important. For some fish they want a territory to defend. If it is having a negative effect, I'd see if the fish seems to be protecting a particular area or decoration. If that seems to be the case, I'd leave that area alone and rearrange other decorations.

Question: Are Legos safe as fish tank decor?

Answer: I don't see why not. Legos don't really have any issues with being in the water. I'd try it. If you notice they get soft spots or start to discolor, I'd remove them.

Question: I just got a fish tank and put everything in it. Now that my fish is in the tank, can put more rocks in it?

Answer: When adding rocks to an established tank, you'll need to be careful. Make sure that you have already cleaned the rocks - usually a rinse with hot water is fine. I would wait until you need to do a water change to add the rocks and I would do it very slowly. If you're talking about gravel, I would add it by the cupful and take the cup of gravel directly to the bottom of the tank to deposit it. If you are adding larger rocks for decoration, I would place them slowly by hand. Adding new rocks and gravel at a water change makes it easier to move things around the way you want them. Remember, fish can stress easily and you want to make this process as easy as you can for them.

Question: I recently bought a 10-gallon fish tank and 9 Mollies. I also have a large collection of shells and rocks which I have collected from various beaches. I have washed them with antibacterial soaps and cleaned them with brushes. Is it okay to put them in the tank?

Answer: Antibacterial soaps can leave a residue, I'd give them a good soak in some bleach water, rinse well, and then let them dry. If you notice the shells starting to break down check your water chemistry, you may see the alkalinity and pH creeping up.

Question: Can I put clay decoration in a fish tank if I rinse and dry it properly?

Answer: I wouldn't. Clay has a lot of minerals in it. When hardened or dried clay can leach minerals into the water, which can mess with the pH of the water.

Question: What should I do if my fish lay eggs and I have to clean the tank?

Answer: What kind of fish do you have? Where did they lay the eggs? You may be able to avoid the area entirely. You could also move the eggs to a nursery tank if you are really worried about losing them. Keep in mind, many species of fish will eat fish fry if given the chance. Do you have plans for the fry when they hatch?

Question: I have some cow vertebrae that I collected a few years ago. They were cleaned with bleach but I have just recently rinsed them and left them in the sun for several days. I read about other people putting bones in their tanks. The bones don’t smell of bleach or anything at all, and as I said it was a few years ago when I collected them. Can I put bones I cleaned with bleach in my freshwater tank? Is there anything else I could do to clean these cow bones?

Answer: The chlorine in bleach will eventually off-gas from objections. Typically, once the object has dried and you can no longer smell the chlorine it should be safe.

Question: Can we use decorative iron in a fish tank?

Answer: Metals can leach out in water. Some fish are very sensitive to metals. For example: the copper in pennies is harmful to elasmobranchs (sharks and rays) and invertebrates. It was a big deal when people would throw pennies into the touch tanks at the aquarium. Iron will rust in water. I would not use iron in my tank.

Question: I have a hundred gallon tank that I've had for about 4 years now. Is it okay to put polyester fabric in a fish tank?

Answer: My gut says no. I can just imagine that it would be very difficult to stay in one spot, would accumulate algae quickly, and I don't think the fibers would hold up to being underwater for so long.

Question: Is there anything special you should do before putting a new fish in a tank for the first time?

Answer: Make sure your tank has been cycled (I have another article on water quality that may be helpful) and has been treated with the proper chemicals, properly acclimate your fish (I like using a drip acclimation), and keep an eye on your fish after you have added them. They will most likely be stressed at first but should adjust to their new home well.

Question: Do I have to clean new store bought decorations?

Answer: I clean everything before it goes in my tank. A nice bit of hot water will help get rid of all the dust and grime before they go in the tank.

Question: I just got a big sunken ship for my fish tank. I rinsed it off and put it into the tank, and I didn't fill it yet when I noticed a strong resin smell. Is this bad for the fish?

Answer: Sometimes new plastics have a smell. Did the sunken ship come from the fish section of a pet store? If so then it is most likely fine, and you can put it in the tank. I recently got a new log for my hermit crab tank that had a strong odor when I opened the bag. The item was listed as safe for aquarium use. I most likely would have given it a rinse or two and let it dry for a few days to let the odor dissipate.

Question: I have 2 fish tanks both with fake rocks and logs. In a search to find some missing shrimp I took out one of the logs and found the shrimp in a large hole in its base and a bunch of grey gunk came out as well. Now I'm concerned about the fake rocks and logs in the other tank. Main concern is fish will hide and die in there, it will turn into a snail factory, or it'll collect waste. thoughts?

Answer: That grey gunk you found is most likely a mix of detritus and algal growth. It happens in fish tanks, especially in nooks and crannies that aren't cleaned often. Every so often when you clean the tank make sure you are cleaning the decorations as well.

Question: Is there a home test to see if decorative rocks are ok in fish tanks?

Answer: I don't know of any such test. I'd say most rocks should be relatively safe as long as they aren't painted.

Question: I just got a rubber plant for my aquarium. I cleaned it, and my betta fish likes to hang out near it, but is rubber bad for fish?

Answer: My concern would be any non-smooth surface of the plant ripping your fish's fins. I would think the plastic of the decoration should be OK as long as you gave it a nice rinse before putting it in the tank.

Question: Is it ok add metal to decorations to weigh them down so they don't float?

Answer: It depends on what kind of metal you want to add. Most metals will rust or decay in water over time. They could also release chemicals into the water which could be detrimental, or fish could eat flakes of rust. I'd use rocks instead.

Question: I washed my tank with hot water and nothing else. Can I put decorations in now, or should I get some special stuff to clean my tank first?

Answer: If you are concerned about past contamination, you can clean the tank with a little bleach water. Make sure that you give it a really good rinse until you can't smell the bleach anymore, and then let it air dry. If it is a tank you just got from the store a good rinsing with hot water and letting it dry should be sufficient. If it is a tank you got from a questionable source or if it's secondhand, I'd clean it with bleach water. It never hurts to be too careful.

Question: I have a hundred-gallon tank that I've had for about 4 years now. Is it okay to put polyester fabric in an aquarium tank?

Answer: The fabric will be a breeding ground for algae and the fibers will start to degrade in the water over long periods of time. I'd stay away from it.

Question: Is an object made of silicone and stainless steel safe to put in a betta tank? I have found that my betta is stressed over the pump (that is already on the lowest setting), so I was planning to try and disperse the water with this object - attached to the wall with suction hooks and zip ties - until he gets more used to it. Are these materials safe for my betta?

Answer: Suction cups are perfectly safe for fish tanks; it's the zip ties you'll need to watch out for. They are fine to be in the tank, but you will want to make sure you cut them as short as possible and that there are no sharp edges. Anything with a sharp edge can cut the body of the fish or rip the fins. The longer the piece of zip tie after you cut, the more of a risk of unintentionally injuring your fish. After you position the zip tie where you want, I'd cut it as close as possible. You can even use a nail file to make sure there is nothing sharp before you put it in the tank.

Question: I have a fake coral piece that I'd like to put in my aquarium. Will it hurt if I put a coral decoration in with a freshwater fish? I was wondering because my goldfish seems to be scared of it.

Answer: No, it doesn't matter. The goldfish don't know that it wouldn't be found in their natural habitat. However, that doesn't mean that they will like it. How do you know they are scared? Will they not go near it? If that is the case, I'd take it out of the tank and see if there is a change in their behavior. Maybe they don't like it, or maybe it's taking up too much room in the tank, and they want more space.

Question: If you have two fish in your tank and you want to add two more, how many days do you wait to buy the other fish and put them in?

Answer: If the fish have already been in the tank for a while and I have stable water quality, I would add the two new fish at the same time. If the tank and/or the fish are new to the tank I would wait a couple of weeks to give my water cycle and fish time to adjust.

Question: Where should I buy a fish?

Answer: That depends on what is available in your area. If possible go to a local pet store and see where they source their fish. Are they captive-bred or collected from the wild? If there isn't anything in your area, see if a major chain pet store has good looking fish. Are they healthy? How far did the fish have to travel to get to the store? I would be hesitant to buy fish online since I can't see them before I buy them.

Question: Are orbeeze safe for a fresh water set up?

Answer: As pretty as they are, I wouldn't use them. If you want a colorful substrate, I would go with colored sand, pebbles, or even those glass half marbles you can find at craft stores.

Question: Could I use Flex Seal Clear to seal an item I want to put into my fish tank?

Answer: I'd be hesitant to use Flex Seal Clear in my aquarium. I'd much rather use silicone. If you go to the manufacturer's website, it says that Flex Seal Clear cannot be used on items that come in contact with drinking water. If I can't use it around drinking water, it won't be in my fish tank.

Question: Can I put a piece of wood in a 2-gallon tank for a beta fish without any filter? It seems my water is cloudy after my water change.

Answer: The wood is going to grow algae like crazy. It will also degrade over time. The wood will also collect old food and fish poop. When I worked with systems with wood at the aquarium the wood was always the hardest part to clean, needed to be replaced more frequently than other decorations, and always made the water filthy after cleaning. I stay away from using wood for those reasons.

Question: Is a glittery background ok or will it be distracting to the fish?

Answer: The fish most likely won't care too much. I bet it will look really cool!

Question: What bottom does a beta fish need?

Answer: They aren't picky fish for bottoms. They are fine with just about any substrate.

Question: I want to decorate my tank with modern (no lead paint) tea cups and make a bubbler out of a child size tea pot. Do you think this will be safe? Everything is glazed and food safe, most is dishwasher safe.

Answer: It sounds like an interesting project. I don't think they're would be any danger in using the tea cups or tea pot, so long as the glaze doesn't start to degrade. If you noticed anything starting to peal off or degrade I'd remove it.

Question: Is a copper decoration ok in a fighting fish fresh water fish tank?

Answer: I try to avoid anything copper in my fish tanks. When I worked at the aquarium, it was always awful when we had to fish out pennies from the touch tanks because the copper in the pennies would mess with the water quality.

Question: Is furnished wood designed for decorating houses acceptable for aquariums?

Answer: For the outside yes. Wood will eventually degrade in water for prolonged periods of time.

Question: what happens if my betta fish doesn't eat?

Answer: Eventually, the fish will die. Now, why the fish isn't eating could be a bunch of different causes. Have you tested your water quality? Poor water quality can stress the fish and cause him not to eat. He could also be sick. Do you notice anything different about his physical appearance? White slimy patches, red sores, or little white dots? What temperature is the water? The cooler the water, the slower his metabolism will be. Bettas are from a more tropical climate. Naturally, they tend to prefer warmer water. It could also just be that he doesn't like the food he's being offered. Try giving him different foods (pellets, bloodworms, flakes, small snails, and so on). He may be a picky fish.

Question: My grandson washed a decoration with soap and water. I know you are not supposed to use soap. He rinsed it thoroughly, but fish are dying. What should we do?

Answer: Have you tested your water quality? It is possible that you are having some issues with NH3 or NH4. It is also possible that there is something wrong with your cycle. If the decoration was rinsed well and allowed to dry before going in the tank, they should be fine.

Question: I have polished geos that look amazing, a glass paperweight and two rocks on top of the sand I bought from the fish store. Is there a way to get these things tested to know if they are toxic? Also, how long do you think it takes to be a problem? This is in the 20gallon tank starter kit from Tetra. The plants came with it. I tested the water and everything is perfect.

Answer: Make sure you are rinsing everything you put in your tank before it goes in. If you want to make sure its clean you can add a little bleach to a bucket and soak the object for 10 minutes, rinse, and let it dry before putting in the tank. I imagine the glass paperweight would be alright in the tank. The geodes might cause some chemistry problems over time depending on what the rock on the outside is comprised of. In aquariums, the decorations are mainly concrete and the concrete does tend to leach chemicals in the water after a few years. However, these chemicals often make the tank more basic which is helpful in saltwater systems, especially if topping off with freshwater is needed. Its sort of a self-buffering system. As far as how much time it would take to start causing a problem in your tank its hard to say. You can try it, but I'd run a chemistry test at least once a week for a month or two. If the numbers are consistent then I'd do a full chemistry test at least every month to make sure the water isn't going too basic, which would be what I would expect the geodes to do over a long period of time.

Question: Can you put fishbowl beads in your fish's tank or not?

Answer: Do you mean the large glass half marbles? Yes, those can be used as substrate. Just do a bit of research to see what type of substrate your fish likes. For example my peacock eel likes to bury himself so he does best in a tank with sand. My beta, however, doesn't care what substrate he has.

Question: How long does it take for a fish tank to get dirty?

Answer: That depends on many factors, including the size of your tank, the number of fish, if you have a filter or not, the size of your filter, the type of fish you have in the tank, the type of lighting on the tank if you have a lot of sunlight on the tank. What do you consider to be dirty? Algal growth, floating detritus, algae covering the glass? Once your tank is set up and you have it cycled and stocked you will get an idea for how often you will need to scrub the glass and do water changes.

Question: Recently, I put a rock about the size of a pebble in my fish tank. I realized after some time though, that it was giving off some tiny bubbles. Is this safe for an aquarium?

Answer: Its most likely air trapped in the spaces between the rocks and as the substrate settles in the tank, the gas is coming out. It's more than likely safe.

Question: Would you consider amber glass or green-colored glass to be painted?

Answer: Colored glass is not painted, that color is a part of the glass and cannot come off. Anything with paint could flake off when exposed to water for long periods of time.

Question: Is Javan Moss unhealthy to humans?

Answer: Javan Moss is a very commonly used plant for aquarium decoration and typically used with cichlid tanks. I doubt that it is unsafe for humans since it is widely used, but it is possible that someone could be allergic to it. If you are concerned about an allergy you can wear gloves when you handle it.

Question: I have plastic plants and a big rock that sits in front of my filter intake (approx. 1”-2” away. Could these obstruct the filtration in the tank?

Answer: Keep an eye on the flow of water around your intake. Do you notice that the plants are being pulled close to the intake? Are your filters not getting as dirty as they used to? If you see the plants getting pulled too close to the intake or that the filters are capturing mach gunk you may want to move the plant. I don't think the rock would block the intake too much.

Question: May I use a natural plant for guppy living in a bowl without a substrate? Which real plant may I use in floating conditions for a bowl with a guppy?

Answer: If at all possible move the guppy to a proper tank with filtration and you can absolutely have a live plant with your guppy. Your fish will most likely enjoy being able to swim around the leaves and look for places to hang out. You'll need some form of substrate to help keep the plant in place, and hide the roots from light. I tend to stay away from floating plants as they can mess with the filtration.

Question: Can paint flaking of decorations cause harm to my fish?

Answer: In short, yes it can. If possible remove the object that has paint peeling off. The fish can try to eat the paint flakes, and that could be harmful to them.

Question: If I have fake plants from a freshwater tank can I add them to my saltwater tank after I clean them in sea salt and hot water?

Answer: Absolutely!

© 2013 Alex

Comments

Tess on August 28, 2020:

Can u add crystals to my fish tank ?and still safe! If not is there a way to treat them to make them fine for my tanj

Coco on August 22, 2020:

Hi I have 4 glofish danios and one octocinclus I am looking to remodel my fish tank. Do you have any sudjestions? Its a 10 gallon tank.

Shemira on August 14, 2020:

do u need to clean lake fish's tank or not cause im having one

Chava on July 28, 2020:

I stopped reading when I got to the point it mentioned gravel cleaning this person is a level 1 aquarium hobbyist. No thanks. Wood rocks clay dirt all that stuff is in nature. Nothing will die with such things in tank . My fish tank and others out there done right are proof

Devaansh on July 15, 2020:

I have a 5 gallon tank, can you please suggest what decorations are good. Thanks!

Carol on July 12, 2020:

Can I add conch shells to my aquarium? The ones I have are 50 years old or more.

Thanks

Alex (author) from Virginia Beach, VA on May 17, 2020:

What are your water perimeters? Also, are you adding any calcium to the water? They have an exoskeleton and may require a calcium supplement added to the water deepening on the mineral composition of your tap water. I had a issue with snails not being able to grow in my culture tank early on and adding a calcium supplement took care of my problem.

Helen on May 05, 2020:

I can not keep shrimp in my fish tank they just disintergrate could you tell me what could be wrong thanks

ABettaLover on April 18, 2020:

@Lucy Maybe you bought color changing stuff.

Lucy on April 11, 2020:

A while back (6-8 months ago) we removed a few ornaments from the tank and rotated a few others into their place. We now want to put the originals back in but have found that they have turned bright purple. I've tried to find a cause online but all I've been able to see is about purple fluffy or slimy fungus. Its not fluffy or slimy or anything physical. It's just all gone purple. as if they were painted that way in the store. Note they were stored dry and were bought from different fish shops and are different brands and none had any shade of purple on them in any way before. My husband tried to clean off the purple with hot water and a scrubbing brush and now they are turning orange. What is it? And are they safe to put back into the tank again?

Maria on April 02, 2020:

Is it possible to make your own tank decorations without harming the fish?

Mike vapormax on March 15, 2020:

can i put a a broken up cup in mu tank

Alex (author) from Virginia Beach, VA on February 09, 2020:

@Puppz123, Yes you can still put in decor when there are fish in the tank. Just be very careful not to squish any fish. You may want to add your decor when you are doing your next water change so the water level in the tank is lower. The fish may get a bit stressed, but they should handle the change well as they will most likely enjoy checking out their new environment.

Puppyz123 on February 09, 2020:

how do I put decor in a fish tank when there's already fish in it? and can I?

Nikkisnona on October 14, 2019:

We changed our albino cats home. He is over 12" and had a lrg log. I changed it to a curved pc of pvc (for plumbing) and he went ballistic. Pushong it n everything else in his tank. Why?

thomas on August 19, 2019:

Can you put jewels and sea glass in fish tanks with fish?

Loftustina on July 30, 2019:

I bought black gravel for my 3 gallon aquatic frog tank. i am a fried he won’t be able to find his black food. should I return the black gravel for a different color?

Boo on July 09, 2019:

This I very helpful!

! Thank you a lot !

jas on May 04, 2019:

I've just put a handful of pony beads at the bottom of my bowl. My fish was spiking around earlier but now seems calmer. The beads are completely plastic. Am I harming her?

Addison Shuttleworth on March 19, 2019:

I don’t know if it is safe to use sculpey clay in aquariums. It’s a bake harden clay.

Lilian on February 26, 2019:

My mollies have recently given birth to 12 fries(babies).2 of them died yesterday.I have placed them in a seperate tank and i change their water after 2 days.What else do i have to do and how long will it take for them to grow.

Also i feed them fish food but sometimes they finish it sometimes they don't.Is it ok.

spaghettisouls on February 18, 2019:

I have a glass coke bottle i got from a factory back in 2015. I know I have to remove the label and glue, but do I have to open the bottle? The pop-off top is metal, so I wanted to be sure before i accidentally killed my fish.

Animalover9 on February 11, 2019:

Can i put perler bead designs in my tank i want to add some shark designs

janet on January 08, 2019:

I have a huge clam shell had it for years if I clean it would it be ok in a tropical fish tank

Lisa12367 on December 07, 2018:

Hey just wondering are fishbowl bead safe to put in a fish tank or just in slime. Because I keep watching slime videos and they do fishbowl bead slime and I keep thinking are they safe for the fish tank. I only have a little tank and I am getting five new fish because my other ones died and I want some new decorations?

Oli on November 24, 2018:

Hi, I've recently got a 20 L fish tank ( #ImmaMetricAustralian), which is the first fish tank I've had exclusively for me. I've had 13 long years past experience, as my family have always had at least one fishy friend swimming around. I'm going for a coastal theme, and have put in some aquarium sand and started cycling with water that was taken from a tank that has been cycling for a few weeks and is ready for fish, other than the fact that there's nothing in it.

Getting to the point (: , I was wondering whether I should replace the sand with sand coloured pebbles now, or gradually add pebbles as i do water changes and gravel cleans. Could you give me some advice?

Sorry about the narrative

Alex (author) from Virginia Beach, VA on November 11, 2018:

@jeremy yes there are glow in the dark decorations you can use in your fish tank. When you go to the pet store these will most likely be with their glow fish products. Some items you may need a black light to get the glow effect.

@ed it is possible it could be from the metal. Some fish are very susceptible to metals. At the aquarium it was a big deal if pennies were thrown in the touch tanks, even though there isn’t much copper in them anymore. Once upon a time people didn’t know that metals where bad and used copper fittings when plumping public arquariums and didn’t know why thei collections kept dying. Tragic, but now when you go to an aquarium if you look behind the scenes all the plumbing is plastic.

ed south on November 08, 2018:

placed a pirate boat on my tank and in a week 6 fishes died. bought it from a pet store. placed magnet on the sais/posts and it stuck. think the iron is culprit?

Lori Ann Lojewski O'Malley on October 24, 2018:

I bought this beautiful ship for my 110 Gal. freash water tank with in A week the paint is fading and I have now lost 7 fish! I took the ship out and got another large replacement shit, man it is just not the same! I love that 1st one so much! Is their anything I can use to seal that ship and make it safe again for my tank. They are made by Penn Plax for fish tank's.

Jeremy Shawn on August 26, 2018:

Hello, are glow in the dark decorations safe In a reef tank?

Alex (author) from Virginia Beach, VA on July 28, 2018:

Sometimes pumps, even on the lowest setting, can cause too much of a current for fish with long tails. Especially when they are in smaller aquariums. If he is the only fish in the tank and you stay up to date on your water changes you may not even need the pump at all. As for the suction cups and zip ties: the suction cups are fine for in tank use. The zip ties are a little trickier. You want to make sure you have them as short as you can and that the are not too sharp. Anything in the tank with sharp edges can cut your fish or rips his fins.

Amber on July 18, 2018:

Hi! I recently purchased a betta from the pet store. He is very active and does not seem scared of ne thing. I noticed he had stress stripes tho so ive been testing his water and checking the temperature like clockwork. One day i forgot and left the pump off after feeding him and it was off for a good 4-5 hours. I noticed that his stress marks disappeared tho. So i am assuming that the pump is whats stressing him out. Only problem is, its already at its lowest setting, and i cant just leave it off. Ive been looking up ways to resolve this and found that it helps to put something in front of it, to sort of disperse the water, so it doesnt make such a strong current (even tho it doesnt really make much current even now). The object i bought is made of silicone and stainless steel. I was planning on attaching it to either side of the wall with suction cups and zip ties. Are these safe to be in the tank with my betta?

Alex (author) from Virginia Beach, VA on June 26, 2018:

If you really wanted to spend the money on diamonds yes, you could put them in your tank. Though, it would most likely look unnatural and gaudy.

Carter K. on June 22, 2018:

Can I put diamonds in my fish tank instead of rocks, or Pebbles?

Chinobandzzz on June 11, 2018:

Can i put gambling dice in my tank?

Sheila Thompson on May 29, 2018:

Colorful rocks peel & paint comes off does It hurt tropical fish??? It seems the fish eats the paint that's floating In the water & they stop moving alot just laying around....

Lynnhankins1@gmail.com on May 20, 2018:

Is it ok to change my fish's decorations every once in awhile.. Will it put stress on fishie. I get bored seeing the same decoratios, but fishie is first and I want him to be happy.

Levi on May 16, 2018:

Danielle, if you have a male betta you can't get any other betta fish. They'll fight and kill eachother. Bettas are aggressive fish. You can have a few females in one tank though, but not more than a few, and not in a 10 gallon. It's too small and even females will fight if the tank isn't big enough. I'd say you need at least 20gal for a female sorority.

You also can't have tetras. They will bite and destroy your betta's fins, male or female doesn't matter. You should focus on researching if fish can even be housed together without incident before you pay attention to their color.

Danielle on May 13, 2018:

I got 2 10gal tanks and had inspiration from a betta. I looked forward to the hobby but after he died i don't know i feel like if i get any other fish thell die too (of corse they will) but sooner than expected. Since he passed i have a empty 10 gal and the other tank has a betta man in it. I don't know if i should get any more bettas since they are fragile and im just a dumb newbie but i don't know what other fish i should get. Maby some hardy fish. Lamp eye tetra and other fish? Im not sure. But for the background i like to contrast fish, like if you have a silver color fish than a black background and dark color fish with a white background.

Nadia Swayib on May 13, 2018:

Are crystals ok to put in tanks?

Alex (author) from Virginia Beach, VA on May 03, 2018:

@Teresa That's very strange. Is the plastic smell coming from the water? Do you have a filtration system on the tank? Is there a hard plastic cover on the filtration system? I would try rinsing with hot water. Just allow it to cool before you add it to the tank. All of those items are meant to be in fishtanks so they should not pose a risk of leaching chemicals into the water. Make sure that you test your water quality before adding any fish. My best guess is that the smell is from the acrylic tank itself, if it is hopefully it will fade with time.

Teresa on April 26, 2018:

Recently I purchased a top fin acrylic 2 gallon aquarium and "Glow" decor, plants and gravel from Petsmart. I rinsed everything thoroughly in cold water. After I put everything in and before I added the water I noticed a very strong plastic smell so I am concerned my betta may be effected. Do you think it will be safe for my betta?

LUZ on March 23, 2018:

I have a 50 gallon thank and I have 4 angel fish, 3 mollies, 2 yellow and black panda mollies, 4 tetra and 2 algae eaters. how often I should change the water and how much, I check the water with the strips to check the levels in the water . and how much of the solution I should put just for the new water or for the complete thank I love my fish and all this so confusing some times. I want to add natural plants but I don know witch ones. I need help. thanks

Nancy on March 07, 2018:

I have a 30 g tank can I put a big seashell that I had for years in it.

Lindy on February 26, 2018:

My kids have a 2 or 3 gallon tank with a female beta. They thought it would be cool to use printer paper to line the outer walls with and cut windows and doors that open. Is it bad to block so much of the fish’s view?

hotshotpro on February 10, 2018:

awsomeness!

Unknown on December 26, 2017:

So much facts. Wow. Mindblown. I regret having the idea of having an aquarium. I´m worrying too much but im sure this would help.

Zach on November 15, 2017:

can you add plastic glow in the dark rocks to the tank. The rocks are about as big as my thum.

Bugles nickname on November 12, 2017:

Is it ok to put a decoration In your fish tank if it isn't in there already because I did that and I took it out just in case it wasn't good for my fish

Cristina on November 04, 2017:

Hi. We are setting up a new 38 gallon tank. I wanted to know if it’s safe to use old aquarium decor from an old tank. Some of the items have never been used, but they have been packed away for several years. Others were used and I would obviously clean them first to ensure they are clean. Any help is greatly appreciated!

taffy on October 16, 2017:

this is a good website because i am doing school stuff with fish tanks

Jared on August 02, 2017:

I was just wondering, I have some glow in the dark paracord and I don't know if it is dangerous to put ina fresh water tank, I would like to, but if I can't, I would like to know that to. Can anyone help?

Alex (author) from Virginia Beach, VA on July 23, 2017:

@Suzi I am not a fan of using bowls for fish homes. They are often not large enough for the fish they contain and are very difficult to put filtration on. You will end up needing to do frequent and large water changes to make sure that they water chemistry does not become toxic to the inhabitants.

That being said, I don't really think the color of the glass is going to effect anything besides your own ability to see in to the tank. Clear glass, plastic, or acrylic is most commonly used because it allows people to see directly in to the tank. If you have glass with a pigmentation you might not be able to see inside as well, or the beautiful colors of the fish may not appear in their full natural brilliance. Aside from that, I really can't think of anything wrong with using green glass. If you have your tank set up, I would love to see pictures of it!

Suzi on July 22, 2017:

Is it okay to use a tank/bowl made out of green glass?

Alex (author) from Virginia Beach, VA on July 08, 2017:

@Riley Let me know how your tank turns out! I love decorating fish tanks. I could get into a lot of trouble at the pet store with all the different decor options.

One day, when I have the room for it, I would love a 150 gallon tank with ancient Greek ruins, live plants, and small schooling fish (like tetras).

Riley on July 08, 2017:

I have two goldfish and I was looking on pintrest for some ideas to decorate the tank. Thank you.

Alex (author) from Virginia Beach, VA on July 02, 2017:

@Meiki Thank you! I enjoy sharing what I know about animals and their care. I've learned a lot in my time as an aquarist. I'm glad you found the article useful!

Meiki Love on June 23, 2017:

Really great information and I appreciate that this is all not just opinions, you are actually basing this off experience. It's hard to find answers when everyone has the approach of just being a know it all. You answered everyone's questions and that's nice. Just read a very informative article and had to give you 5 betta fins up for being awesome and truthful.

Alex (author) from Virginia Beach, VA on June 07, 2017:

@Kim How long did you wait after you set up your tank before you put the fish in? It is possible that the tank had not fully cycled before you put the fish in. While the tank is cycling the good bacteria are building up in the filtration and in the gravel. This is exactly what you want to happen in your tank, they will allow the nitrogen cycle to work in a timely manner. Try to refrain from major water changes are changing out the gravel too often, this could kill off too much of the good bacteria. If that happens your tank will need time to rebuild it's cycle.

Bacteria blooms will also happen while the tank is cycling, the water may appear to be cloudy during a bacterial bloom. Neon tetras are not the hardiest of fish and would not be a good choice for the first fish to add while a tank is still cycling. If I had to guess I would say the tank had not fully cycled and the tetras could not handle the stress of fluctuations in nitrate, nitrite, and ammonia levels in the water.

Investing in a full water chemistry set is a good idea if you would like to learn more about water chemistry. The test strips are fine, but they are not as accurate as the sets with the test tubes. For more information about water chemistry and the nitrogen cycle check out this article here: https://hubpages.com/animals/Practical-Fish-Keepin...

Best of luck! Fish keeping is a great hobby and can be very rewarding, it just takes a little time, effort, and research.

@Mike Well, for starters legos are not made to go in fish tanks. It is possible that chemicals could leach out into the water and affect the water chemistry. Worst case scenario it could kill the fish. However, I am not so sure how dangerous legos are for fish. When I worked at the aquarium we would use all kinds of plastic 'toys' in the tanks. Dog kong toys were used to hold lettuce for fish to browse on. Lots of different kinds of children's toys and dog toys were used as enrichment for the octopus and other fishes. But, these items did not stay in the tanks for long term. We're talking maybe couple of hours at the most and never for days on end. Those toys were also clean with hot water and dish soap and then bleached and allowed to air dry for the chlorine to off-gas. I would imagine the legos would float in the fish tank, and would therefore not be suitable for use as fishtanks decor. To be safe, I would stick with something that has been made for use in a fish tank. Hope this helps!

Mike Fleary on June 03, 2017:

My friend built and put a sleeping place out of Lego's for his beta fish and I keep telling him to take it out. I need some facts to convince him to take it out.

Kim on March 15, 2017:

I bought a 10gal aquarium about 6 months ago I had bought 4 glow fish and 2 neon tetra and the black light for the glow fish. The glow fish would hide under the filters and then after about 1 week they started dying I tested the water with the test strips and it was fine I went to petsmart with a water sample they said it was fine and replaced the fish about a week later it happened again so I got different fish 2 none tetra 2 red lid tetra and then petsmart sold be a bunch of chemicals for the tank I have done complete water changes bought new gravel and my fish keep dying please help

Daniel D.- A fish expert on February 26, 2017:

Never buy those one fake jelly fish with the sting that you can attach with a suction cup. One time I bought one because I thought it looked cool well......... I had it and one day I looked at my fish tank and one of the fish had gotten caught in the string and died.

Alex (author) from Virginia Beach, VA on February 15, 2017:

@Madison I have not heard of goldfish being aggressive to other species of fish. I would stay away from betas and gouramis, since they can be aggressive and nip the fins of a brightly colored or long finned fish. But, I would imagine that you would be able to keep medium sized tetras, cory cats, or loaches. You make sure that the other fish are getting all the food since goldfish aren't known for being the fastest fish in the tank. One great thing about the telescopes is that they can tolerate a wide variety of water temperatures, so they are very flexible when it comes to the water parameter needs of their tank mates. Make sure that you have an excellent filtration system on your tank! All goldfish are known for being messy.

@Mickey Be careful about adding woods. You will want to make sure that it doesn't have any staining on it since it will leech into the water. Wood itself is fine for a tank, just keep in mind the wood will grow algae on it and will need to be cleaned periodically. Also, overtime the wood will degrade and breakdown. Since wood is a porous matter I would not pre-treat it with bleach before putting it in the tank. I would soak it in hot water, not boiling, but hotter than tap, for a little while to kill anything that may be living on it.

Mickey on February 13, 2017:

I have an ornament that I would like to use in my tank. It is made of wood. Can it be treated to make it safe for my fish?

Madison B. on December 20, 2016:

Hi, I was wondering if there are any fish besides goldfish that I could put in a tank with a black telescope and a calico fantail? I would love a lot of variety with the types of fish and I want the fish to be really the stars of my tank.

Jack on November 27, 2016:

Very nice post! Decorating my tank was probably the most fun part of setting up my aquarium. I like your little bit about choosing substrate and how sand can be difficult to work with. I used to use sand for one of my tanks and eventually replaced it all with gravel since it was a chore to clean out.

Brandon on October 28, 2016:

My fish is molly fish...so how many time should I feed them per day and put how many food? thanks.

Alex (author) from Virginia Beach, VA on October 26, 2016:

@adam sounds like your tank is around 5 gallons. I would personally add a small airstone with a small air pump. You can get one from the store or online that is for 10 gallon and smaller tanks and that would work just fine for your fish. It's better to have the airstone than to not.

@brandon what kind of fish are they? Different species have different rates of metabolism. I would watch your fish the next time you feed them. Are they able to eat everything you put in? Did they lose interest before the food was gone or were they still looking for more when it was gone? Depending on the type of fish it might be a good idea to give them some food in the morning and at night. Hope that helped!

Adam on October 26, 2016:

Hi, I have a 20cm x 10cm rectangular small fish tank and inside I feed two about 2 to 3 inches fishes inside. May I ask that I need to put air pump or not because I heard they said that it didn't have much enough of oxygen in water for the fishes......is there other way to make sure the water have enough oxygen or must put air pump into my small fish tank? Thank you.

Brandon on October 26, 2016:

Hello, I have two small fish about two to three inches only. May I ask if I give them food once a day and only a few like six to eight of the fish food grain to them is it enough and ok to my fish ? Thanks.

Alex (author) from Virginia Beach, VA on October 25, 2016:

@Kai, I would give the rocks a good wash before I put them in my tank. I would rinse them in hot water for a few minutes. If you think they could have something harmful to the fish on them you can soak them in bleach water for ten minutes, give them another good rinse, and let them dry completely before putting them in your tank.

@Corey, there are fish that betas will get along with. Neon tetras would be a good match if the tank is big enough for more than just your beta. With betas you don't want any long finned fish (no mollys!), or another kind of labyrinth fish (no gouramis). But an algae eater or bottom fish (think cory cat) and neon tetras would be good tank mates.

@Elton I would add some sort of decorations. You want the fish to be comfortable in their environment. Adding a substrate also increases surface area for good bacteria, this will help your cycle. And having plants, live or fake, will give the fish places to hide and make them feel better in the tank.

Elton on October 25, 2016:

Hi, I only feed two poecilia sphenops (molly) fish in a small plastic tank and this is my first time, so may I ask that should I put some small pebbles and fake grass in it for decoration or for the fish breeding?

Corey on October 24, 2016:

Hello,

I have a Male Betta. It seems like he gets lonely at times.. is there ANY type of fish that would be okay to put in with him?

Thanks

Kai on October 18, 2016:

Hi I'm a somewhat beginner, I've done hours of research on new freshwater aquariums and whatnot, but I've only ever had a fish tank when i was little and don't really remember much from then. I have a huge rock collection and would like to put some of those rocks into a new tank. How can I make sure that there is nothing on the rock that will mess with my tank? Is it possible to put them in the tank when cycling it before actually putting any fish in and testing the water? Thank you

Alex (author) from Virginia Beach, VA on October 17, 2016:

@HuzaifaMotiwala. I don't think the money plant will live very long completely submerged in water. The plant itself wouldn't be harmful, but as it dies it will mess with the nitrogen cycle. If you can get the money plant to grow hydroponically then you might be able to have the roots in the tank and the tree part on the outside. It would look cool to have little neon tetras swimming around! But, I am not familiar with growing this plant hydroponically, so I don't know if it will work out.

@Annonymous, I honestly don't know if they will be safe to use. I checked out their website and they sound like they are well made. I would say you can give one a good rinse and give it a shot. I would keep an eye out to see if the paint starts to chip off or if the figurine starts to degrade at all. I think it could be worth a shot!

HuzaifaMotiwala on October 07, 2016:

Can I grow money plant in my aquarium?

Is it harmful for fish ?

Alex (author) from Virginia Beach, VA on August 30, 2016:

@gerry when I worked at the aquarium we would bleach everything (10% bleach to water ratio) after it came out of a tank. We would soak it for at least 10 minutes and then it would go into a bucket with a thio/water mix, and then we would dry it. At home you can use a splash of bleach, let it soak for a few minutes and then rinse with fresh water until you don't smell the bleach anymore. I would then let the ornaments dry completely, if there any chlorine left of them they will offgass while they dry.

As long as the ornaments are not made of a porous material you should be fine if you bleach them. In the future I would not use dish soap to wash them as it could cause problems if you do not get all of the soap off. A hoot soak in some hot water or a little bleach water should be all you need. Hope this helps!

Gerry on August 29, 2016:

I broke down my tank and cleaned it to start over. I soaked the tank ornaments in dawn dishwashing liquid. The owner of the fish store I buy fish from said I should never use dish cleaner. It will kill the fish, he said. Do I have to throw all the ornaments away? Is there something I can wash those ornaments with that will neutralize the soap? I have been soaking them in plain water for the past two days.

Anonymous on August 01, 2016:

Is it safe to use Schleich model animals as decorations in a fishtank?

qq on July 22, 2016:

what are those

Alex (author) from Virginia Beach, VA on July 01, 2016:

@Andy, make sure that any foam you use will not leach any chemicals and is nontoxic when dry. That can be a problem with concrete over time as well. Depending on the size of your tank and the size of the item you are making it could be an issue for your system as the concrete will leach chemicals that will make your tank more alkaline in nature. (Which can be helpful if you have a large saltwater system.) I am not too sure about the styrene, but my gut says to leave it out of the tank. It might be better to use the styrofoam to make a mold and the fill the mold with an acrylic like material. Hope this helps!

@Anne, I would advise against using metal in a fish tank. The rust will mess with your water chemistry and if the fish eat any of the rust flakes it might not be too good for them. Once the stand starts to rust it will continue to erode away. A plastic stand that is not painted would be a better option in my opinion. I'd love to see a picture of the finished product! It sound like a really neat idea. Best of luck!

Anne on June 27, 2016:

Long story short, I would like to put a very simple metal plant stand into my 55-gallon tank (5 fish) for decorative reasons. Will the metal or perhaps rust be harmful to my goldfish?

Andy on June 27, 2016:

hi, are there any materials like styrofoam or polystyrene that can be carved into shapes, glued together and covered in concrete!? I know the silicone/glue needs to be safe as well as the concrete but I'm not sure about the styrene or foam!?

Betsy on March 27, 2016:

Very good condition

Alex (author) from Virginia Beach, VA on September 13, 2014:

They do sell dividers so that you can do just that. However, no two fish are exactly alike. One of my roommates in college had a beta tank with a built in divider so she could have two bettas. One of them would always flare his gills and try to attack the divider, the other fish didn't seem to care after the first week. It's possible that if they can still see each other they might behave in a similar fashion.

Personally, I wouldn't put a divider in my tank. I don't think they look very appealing and I don't want to stress my fish.

kim on September 12, 2014:

can u separate the tank so you keep bettas apart or should u do it so they don't see each other also

Sp Greaney from Ireland on August 26, 2014:

I think it's nice to add decoration to your fish tank as it makes it looks less sparse. I think purchasing items for your tank in pet stores is ideal as you know that they are safe and meant for that specific purpose. It would be awful to put something in there that you shouldn't and end up killing your fish. Nice hub.

Melanie - Texas on August 04, 2014:

Thank you for your reply. After years of not having problems, this did all start when I added the decoration. I got 7 guppies and a male molly too at that time. Some of the guppies had babies, then they all died except for one male. So did the mollies (I already had a female). Even one of the red-tipped finned tetras died, but the other 3 remain. One cory catfish died, but the other catfish are fine, including the Plecostamus. Today I notice the male guppy "feels better," when he seemed somewhat distressed before. It seems all the babies are doing fine. The tank is a 30 gallon. I had put one dose of ich Rx in there, then afterwards, some dissolving fungus pills, as a safeguard. Then it said wait a few days and do a water change before adding more pills. I'm waiting and watching to see if I even need to do that again. I had noticed one fish with a tail problem, but it could've been bitten as well. But that fish did die. The only sickness I noticed was horizontal positioning and gill inflammation, and wriggle waggle distress. What gets me is that the decoration was there, in the pet store, for aquariums. Why would they be selling things that can poison your fish?

Alex (author) from Virginia Beach, VA on August 03, 2014:

Have you tested your water quality? But, I do agree that it is most likely the new object that you added. Do you still have any living fish in your tank? I think you are on the right path and agree with removing the decoration. I would treat your tank like it is new again. Add new fish slowly and in small numbers. Keep an eye on your nitrogen levels. If there is any toxins still in the tank from the decoration it should disparate with time and water changes.

Melanie - Texas on August 03, 2014:

I bought an ornament intended for aquariums at the pet store, at the same time I bought some new fish for the mature tank. I added some Rx to the tank, as I always do when adding new fish. Fish began to die. I couldn't see any symptoms, like ich or fungus. After awhile, I noticed the painted ornament was turning green (from brown). I saw that the paint was chipping, and it scraped off with a fingernail (while wet). I've removed it. Could it be that the ornament has been poisoning my fish? I did about an 80% water change and cleaning. Is there anything else I can do? Thanks