Eric is an aquarium enthusiast with over two decades of experience caring for a wide array of tropical fish.
Aquarium Filtration Explained
A good filter is one of the most important parts of your aquarium setup, and keeping your tank water clear and clean is one of the keys to happy, healthy fish. Needless to say, choosing the right filter will go a long way.
An aquarium filter has several jobs:
- Catch any debris that gets sucked up through the intake tube. This is called mechanical filtration, and most filters use some type of sponge or pad to prevent debris from flowing back through the filter and into the tank again.
- Provide a means of chemical filtration. This is where certain substances such as activated carbon are introduced into the system in order to manage waste chemicals created by the aquarium inhabitants. This is usually accomplished via cartridges or inserts placed directly into the filter itself.
- Facilitate biological filtration. This is where natural bacteria accumulate in the tank and assist in breaking down ammonia and other harmful chemicals. These microorganisms live in the substrate, on plants, rocks, and decorations, but also inside the filter. Most filters provide some kind of surface to make it easier for them to take hold.
- Create a gentle current to circulate water around the tank. Good circulation means the heat will be distributed evenly, the water will be properly aerated and less debris will be able to sink to the bottom of the tank.
In this article, you will read about a few recommendations for filters that meet all of these criteria. The filters we’ll look at in this here are all hang-on-back, or HOB, filters. They are the most common type of filter in the aquarium industry, and widely available in pet stores and online. While there are more advanced systems out there, these do the job just fine in most aquariums.
I’ve used each of them at one point or another, and they were all very effective. All are available in models for 10-gallon, 20-gallon, 30-gallon, and 55-gallon tanks, and some even larger fish tanks.
Choosing and caring for a quality filter is one of the most important aspects of aquarium maintenance. If you are ready to move up from the standard filter that came with your tank, or if you need a replacement, here are a few to consider.
Tetra Whisper Power Filter
My first and simplest recommendation is the Tetra Whisper Power Filter. Tetra is one of the biggest names in the aquarium industry, and their filters are very popular. As the name suggests, one of the biggest positives about them is their quietness. While no filter is truly silent, and there is always at least a slight gurgle, I was pretty satisfied with the noise level here.
This filter utilizes a cartridge system and comes with Tetra's Bio Bag, which provides all three stages of filtration in one handy insert. These are super easy to use for most causal aquarium hobbyists, and there is more space in there if you want to add your own filter media.
Bio Bags are sold in replacement packs as well, and they are fairly inexpensive. When one gets dirty, you simply remove it and replace it. It’s best to do this on a set schedule before things get too messy.
I used Tetra filters for years on my tanks and never had an issue with them. They are reasonably quiet, and it’s easy enough to replace the cartridges when they get gunked up. I’d say this filter is best for tank owners who want minimal hassle and appreciate the simplicity of the cartridge system.
Marineland Penguin Power Filter with BIO Wheel
Penguin filters by Marineland work on the cartridge system as well, but with a little twist. Like the Tetra filter, they have disposable, replaceable filter cartridges. In this case, they are called the Rite-Size Cartridge. They are inexpensive and easy to replace when they get dirty, and by themselves, they provide a solid level of filtration. But this filter also has a snappy design that incorporates a water wheel.
Marineland calls it the BIO-Wheel, and it serves a purpose aside from looking really cool. The idea is that healthy microorganisms colonize the BIO-Wheel, and as the water flows over it any residual chemicals that linger after the filtration process are taken care of.
The Penguin filter with BIO-Wheel looks cool, sounds nice, and gets the job done. It is definitely one of the best aquarium filters you can choose for your tank.
There is no doubt the Penguin is a unique filter in this review, and I used them for a long time. I really like the BIO-Wheel design, but it does sometimes create a soft gurgling sound, especially when water levels are a bit lower. I found that pleasant, like a quiet brook.
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Penguin Aquarium Filter Maintenance
AquaClear Power Filter
This AquaClear system does not utilize a cartridge but instead features a basket where you can place whatever filter media you like. It comes with a sponge for mechanical filtration, an activated carbon pack for chemical filtration, and their BioMax insert to assist with biological filtration.
Replacements for all of these are readily available, and AquaClear also makes other inserts that work with this filter.
I’ve used this filter on my most recent tanks, and I really like the flexibility. With artificial plants, I use all three of the filter inserts provided with the filter. In the past, when I had real plants in a larger tank, I simply used this filter plus two sponge inserts in the basket.
This fulfilled the mechanical filtration aspect, and I relied on the plants and substrate in the tank for the rest of the filtration. If I were to make the move to live plants in the future, I would probably go back to a similar filter setup using the AquaClear.
With the AquaClear you have options. It’s a great choice for any level of fish keeper, but those who have been around the hobby a little while may especially appreciate it.
More on the Filtration Process
Choosing a good filter is a great step in making sure your tank water is safe and your fish are healthy. But there are other things you can do to help the process along. Don’t rely on your filter alone to do the heavy work. Take some proactive steps in keeping your tank clean.
Weekly Water Changes
Performing a weekly partial water change is one of the best things you can do to keep your tank water healthy. By removing about 30% of the aquarium water and replacing it with fresh, clean water you are diluting the harmful chemicals.
Monthly Deep Cleanings
Combat algae and the accumulation of detritus atop the substrate by performing monthly deep cleanings. This means performing a water change, plus vacuuming the substrate, cleaning algae off the glass and decorations, cleaning out the filter, and replacing any cartridges if necessary.
Utilize Live Plants
One of the very best things you can do to keep your tank water healthy is to include live plants. Plants will suck up the harmful chemicals produced by fish and decomposing food like a sponge, and it will be like fertilizer to them. Plants help a lot, and you may find, as I did, a well-planted aquarium needs little in the way of filtration aside from water movement.
Over-filter if Necessary
For very large tanks, and in the absence of live plants, some fishkeepers like to over-filter. This means you’ll be using two filters instead of one, with a combined water flow rated quite a bit higher than your tank generally requires. It’s just an added measure to make sure the water is clean.
For most tanks, one filter is plenty. If you stay on top of things you should have no trouble keeping your aquarium safe and healthy for your fish. Choosing the best aquarium filter is a big step in that process.
Water Change Poll
This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.
Eric Dockett (author) from USA on June 20, 2020:
@Matt - I usually only consider over-filtering for larger tanks. I'm not sure its a great idea for a betta tank since they are so affected by the current. For 5 and 10-gallon tanks I think I'd stick with a properly rated filter.
Matt on June 19, 2020:
I'm thinking of setting up an aquarium, possibly having a Betta in a 5 gallon, or, possibly, a Betta and 5 or 6 Cory Catfish in a 10 gallon - thoughts?
Also, I've read a lot of your articles and you often mention over filtering on a tank that is 10 gallons. Do you many suggestions for a tank and a filter because most every tank I've seen only has a filter that filters the exact space that the tank is when it comes with the tank.
Any ideas for mixing and matching a 10 gallon tank with a a great filter?
Also, when looking at bigger filters on a 10 gallon tank that holds a Betta, would the flow be of any concern?
Thanks in advance for any helpful info and tips you can provide me with!
Eric Dockett (author) from USA on May 27, 2017:
@ Ariel: It depends on the size of the tank and how much water you are changing. If you doing a full water change of course you'll need to move him while you work. If you are simply using a siphon to remove water and refill, he can stay right in the tank.
Ariel/H2O on May 23, 2017:
do i need to take the fish out of the tank before i change water or ?
Mrbb922 on April 16, 2016:
@Mars Firstly gold and koi fish are among the dirtiest of all fish through all types (cold, tropical, brackish, black, marine). They like most bottom feeders or "clean up" crews actually produce the most amount of waste. But this could of been caused by alot of other factors as well. Firstly how much are you feeding? Personally the 2 minute rule is b.s. You should feed very little 2-4 times per day. Remember fish don't have breakfast lunch and dinner, they are opportunistic and eat throughout the whole day. Secondly how much light are you allowing? Remember that if it's near windows sun light must be added into account for algae and bacterial blooms. Thirdly how long did you cycle? Most people believe fish can be added right away, even if they bought the so called "beneficial bacteria" water supplement. This is also untrue. You can't just add something expect a healthy colony like magic, it must cycle. Lastly the biggest downfall of most aquariums is the hobbyists. Lack of patience, over cleaning, introducing chemicals through various means. Just a few tips, always use hot water no soap to rinse up to elbows before sticking hands in. Ditch the carbon as when it absorbs all it can will leech it back into water and is essentially USELESS for aquariums other than for medication removal. Go with a sponge or foam pad in course medium fine layout. This will trap larger debris before reaching the fine floss that will hold much more benefical. Remember your filter holds the most beneficial bacteria in your tank and when you remove cartridges you remove your colony. Just rinse the sponges or foam in tank water you pull out during water changes to unclog. These only need changes every 1-3 years. Also never gravel vac entire tank do 1/2 of it every water change. And live plants can harm a tank if you don't have proper co2 exchange stay away from plants unless your read up and prepared to. Airstones don't do what people think, the bubbles do not add oxygen, the surface disturbance does. It releases co2 and allows oxygen to be basically ducked back in. Switch to gentle powerheads or an extra filter for the added surface distubance. But account for your lights, motors of all equipment, including bubbler pushing ambient air into your tank. Which in your case should be cold for fish meaning quite a bit lower than degrees. Most larger koi/goldfish tanks have chillers on them which even bring them down to just above freezing. The added heat could be stressful on your fish.
Eric Dockett (author) from USA on October 02, 2014:
Thanks for your feedback, Mars. Sorry to hear about the bad experience. I've personally never had any trouble with Tetra filters.
Mars on October 01, 2014:
I recently started a new 10 gallon tank that came with a Tetra Whisper 10i and am ridiculously disappointed. I have two young koi fish that are relatively clean, but just in a day or two the tank was cloudy. I don't recommend that filter system at all. I just ordered the filter system I have on my other tanks and will be throwing that monstrosity out as soon as I get it.
sheilamyers on February 05, 2014:
You could also call this hub "All the answers to the questions you were afraid to ask". When I bought my tank it came with an AquaClear filter so I never bothered checking out any of the others. After a couple of moths I did come to realize the one they sold with the set-up wasn't quite big enough for my 28 gallon tank, so I replaced it with the next size up AquaClear. To save some money, instead of buying the inserts, I bought a large bag of the filter floss and a plastic jug of activated charcoal.
Eric Dockett (author) from USA on February 04, 2014:
Thanks Ann. I do agree about the aeration.
Ann1Az2 from Orange, Texas on February 04, 2014:
I, too am fond of the bio-wheel, but the one I was using finally broke on me and by that time, I had gotten a bigger tank and so went to the Tetra Whisper. I have it on all 3 of my tanks. Good information in this hub. As you probably have discovered, though, aeration is the most important thing - I have additional aeration in all of my tanks, through decorations and air stones. Live plants, like you say are excellent, but I never got into them. Maybe one day! I voted this up.