Eric is an aquarium enthusiast with over two decades of experience caring for a wide array of tropical fish.
Small Freshwater Fish for a Mini-Aquarium
Keeping fish at home is a hobby practiced by millions of people around the world. For a long while, the only small container available to house fish was a bowl. Small tanks and micro-filters could be had by those willing to track them down, but for the average consumer, there were few choices.
Apparently spotting a niche, aquarium supply companies began to manufacture little tanks that can easily sit on a desktop. They are usually acrylic, and they come packed with everything you need to set up a functional aquarium.
Most commonly, mini tanks come in one, two, three, and five-gallon sizes. These are very small tanks, and your stocking options are minimal. If this is the kind of tank you are interested in, my advice is to ignore the smallest models and go with at least a 5-gallon tank. While still small, at least you have some options, and if you do it right you won't compromise the health of your fish.
This article will help you choose the right fish for your small tank. But, just because these animals can survive in a small aquarium doesn't mean they are easy to care for. If you are new to the fish-keeping hobby you may want to first read my post on the best tropical fish for beginners.
Why Choose a 5-Gallon Tank?
A 5-gallon tank provides some good stocking options, and the best ones are built to accommodate an appropriate filter, heater, and lighting setup. It's still a very small volume of water, but enough so that a simple maintenance schedule can be established and the tank can be kept clean with minimal effort.
Five-gallon tanks don't take up much more room than those mini tanks and are small enough that they don't need a special stand. The 5-gallon tank allows kids (and adults, too) to get a better view of fish behavior. They are suitable for creating micro-ecosystems you'd never be able to establish in a smaller tank. This, of course, is much better for the inhabitants of your tank, but also for children who can enjoy the educational benefits of aquarium care.
The bottom line is this: The smaller the tank, the more limited your options. A 5-gallon tank will give you the ability to house species you could never care for in a tiny one, two, or three-gallon tank.
Top 5 Fish for Your Small Tank
As you now hopefully realize, there are very few tropical fish that can do well in a very small tank, and a 5-gallon setup is much better than those tiny aquariums. Even betta fish aren't appropriate for little one-gallon tanks. But there are a few options out there for 5-gallon tanks, some fish and some not.
No matter what fish or critter you are interested in, you should consider the largest tank you have space for. Just as a 5-gallon tank is better than littler aquariums, you'd be better off still with a tank of at least 10 gallons.
Choose wisely, don’t over-crowd, and make sure you clean the tank weekly. Here are five ideas for stocking your small aquarium.
1. Betta Splendens
A single male Betta is a great choice for a small tank. Give him some decorations to hide in and swim through, and make sure the current isn’t too strong. He will not need the filtration if you keep the water crystal clear, but if it isn’t bothering him you may as well leave it on.
If you choose a male Betta for your tank he should be in there alone as there is a strong chance he could be aggressive in such confined quarters. Though, in a larger tank, he may get along fine with community fish.
A word of caution: If you plan on a Betta fish please take the time to learn how to care for him correctly. You can start here: Betta Fish Care Facts and FAQ
2. Fancy Guppy
Guppies are small, curious fish and will do well in a 5-gallon tank, provided the water is warm enough and the environment is kept clean. They come in all kinds of different colors, so in combination with your aquascaping they can make your tank quite an eye-catcher. Stick to a conservative school or 6 or fewer with these little guys. Even though they get along, you don’t want to overcrowd.
If possible, do some research (or ask the staff at your pet store) on how to tell male and female guppies apart. It is a good idea to stock two females for every one male in order to cut down on stress.
3. Neon Tetras
Little neons (and other tetras) aren’t a bad choice for a small tank. Like guppies, you’ll want to choose a school for five or so, with no other tank mates. With neons, it is especially important to keep the water clean and clear, as they can be sensitive. If you don’t already have one, I suggest getting a freshwater test kit so you can monitor water parameters in your tank. The waster in a small tank can go bad quickly if you don’t stay on top of things.
I’ve used the API Freshwater Master Test kit with a lot of success. It’s easy to use and lasts a long while. It offers peace of mind, as you don't have to guess whether or not your tank water is healthy for your fish.
4. Zebra Danio
The zebra danio is another small fish you can consider for a 5-gallon tank and stock in a school of five. They are a little hardier than most of the other fish listed here but don’t let that convince you that tank management doesn’t matter. You’ll still want to keep the water clean and ensure your fish have the best possible living situation.
You can also check out zebra GloFish if you are interested in something off the beaten path. These are zebra danios that have been genetically modified to show some crazy, neon colors.
5. Dwarf Gourami
A dwarf gourami is a bad choice for anything less than five gallons, but if that’s the tank size you’ve chosen it may be an option. Gouramis are anabantids, meaning they can breathe the air above the water.
Bettas are also in the anabantid family, which is why they can do well in water with lower oxygen levels. But that’s no reason to let the tank get dirty. A dwarf gourami requires clean, warm water and should be kept alone in a 5-gallon tank.
Remember that dwarf gouramis are considered semi-aggressive fish. I will reiterate that it is not a good idea to have tankmates with a single gourami in a small tank. Also, realize that there is a big difference between a dwarf gourami and other gourami species, so choose your fish carefully!
Critters for Your Small Tank
You might want to skip fish altogether and stock your small tank with critters instead. Here is a couple you might consider:
African Dwarf Frog
Most small aquariums come with secure lids, so the African dwarf frog may be a fun choice. They don’t need super-warm water, and they are amphibians so they breathe air. But they do need clean water and plenty of hiding spots. African Dwarf Frogs can be kept in a group of two or three in a 5-gallon tank.
Also, don't forget about the secure lid thing, because they can and will make a break for it.
These little shrimp are often thought of as food for other fish, but they are interesting critters in their own right. You can have a little group of half a dozen shrimp in a 5-gallon tank, provide a lot of interesting things for them to climb on, and feed them algae wafers and sinking pellets. It would make for an intriguing if unconventional tank setup.
Are Goldfish Good for Small Tanks?
Goldfish are generally not a good choice for such a small tank. Most goldfish grow much larger than you may realize, and they need more space than a tiny tank.
They are also dirty fish, and will quickly pollute such a confined environment. That said, if you have to choose between keeping a goldfish in a bowl or a 3-gallon tank, the small tank would obviously be the better option.
Advice on Setting Up Your New Tank
Caring for Your Fish
Keeping fish is a rewarding experience. Unfortunately, too many people see tropical fish as disposable pets and don’t fully consider their needs. Please do not overstock a small tank, or add fish that are clearly unsuitable. This is bad news in any tank, but especially in smaller tanks things can quickly spiral out of control.
There are a few things you might want to think about before choosing such a small tank.
For one thing, you are typically unable to choose your own aquarium filter for many mini tanks are very weak, and only slightly better than none at all. Often it’s a poor under-gravel system: Just an air pump pushing bubbles through an air stone lodged in a tube which creates a current that will hopefully suck debris down into the substrate.
All tanks require regular water changes, but this type of filtration requires frequent cleaning, probably to the point of removing the gravel once a week and rinsing it. In such a small tank any waste can build up to dangerous levels very fast. But if you’re willing to put up with the work, at least the bubbles serve to oxygenate the water.
These tanks also rarely come with heaters, a must for tropical fish. If the air temperature in your home is steadily in the mid-70s you don’t need a heater, but otherwise, your choices of fish are limited. The light that comes with the tank will warm the water somewhat, but not nearly enough in cooler environments.
Remember that by choosing to keep fish or any animal, you are entering into a contract as its steward and caretaker. Your fish are completely dependent on you to care for them in a humane manner and to make sure their needs are met. Sure you’ll make mistakes, and you’ll probably feel bad when you lose a fish because of something stupid you’ve done. But we’ve all been there. There is a difference between making an honest mistake and willfully endangering an animal.
If possible it’s best to upgrade to a larger tank, at least ten gallons, that can better meet the needs of your fish. But if you are set on a small aquarium be sure to choose your fish wisely, and take good care of the tank. You’ll be a happy fish keeper, with happy fish.
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.
Questions & Answers
Question: Which fish would be good for a one-gallon tank?
Answer: Betta fish are the only fish even remotely appropriate for a one-gallon tank. Because they are anabantids they can breathe air from the surface, and they can survive in less-than-ideal conditions. Small, one-gallon tanks often have poor filtration, and they pollute quickly, meaning most fish will perish.
But even the betta isn’t really a great choice. In fact, in my opinion, no fish should ever be kept in a one-gallon tank. I suggest at least a 5-gallon tank or bigger for bettas, and I would prefer you choose a 10-gallon or bigger for every other species. It gives fish enough room to swim, and it gives you better options for heat and filtration.
It isn’t possible to learn how to care for an aquarium properly with a tiny tank. Bigger tanks are easier to care for, and give you a greater chance at success as a new aquarium owner.
You may be tempted to consider a goldfish for a one-gallon tank, but they are not appropriate either. All varieties of goldfish grow much too large for such a small aquarium. They also pollute the water very quickly in a confined space. Goldfish should be kept in very large tanks or ponds.
Question: How many 3-inch goldfish can live in a 5-gallon tank?
Answer: One goldfish could live in a five-gallon tank. I would not try to keep more. Because of their physiologies, goldfish pollute water quickly. One fish and a good maintenance routine will be fine for the short term.
However, if the question was how many goldfish<i> should</i> live in a five-gallon tank the answer is: <i>zero</i>. Most species of goldfish grow very large, believe it or not, and require huge tanks or outdoor ponds as adults. Even a common goldfish can surpass a foot in length if allowed to reach its full potential; obviously much too large for a 5-gallon tank.
Recommended for You
If you haven’t yet purchased a fish for your tank, consider a betta fish instead. They are appropriate for 5-gallon tanks, where a goldfish really isn’t. If you have your heart set on goldfish, take some time to research their true care requirements before you get one. If you start out with a juvenile in a 5-gallon tank, have a plan to move it into a more appropriate environment as it gets older.
Eric Dockett (author) from USA on July 01, 2020:
@Amy - I would prefer to see all these fish in a 10-gallon or larger, which I mentioned in the article. There is nothing wrong with keeping zebras in a 20-gallon tank, and bigger is always better, but it is not a minimum requirement.
Amy534 on June 30, 2020:
What are you talking about? I know for a fact that the Zebra Danio need at least a 20 gallons tank.
ehzaaz akbar on June 29, 2020:
i have a 10 gallon tank and i am thinking of putting guppies and plecos. there is a filtration and heating system as well
Eric Dockett (author) from USA on May 27, 2020:
@Unknown - Then perhaps fish keeping isn't for you. The cost of a 5-gallon tank isn't unreasonable, and if you hunt around you can put one together for around the same cost as a 1-gallon kit.
Unknown on May 26, 2020:
You think we got the money for all that? One gallon is enough in my opinion for small fish. I'm not rich, I surely can't afford a 2 gallon and up.
Eric Dockett (author) from USA on December 24, 2018:
@Becky - There are several commonly available tropical fish that go by the name "shark" , including rainbow sharks, bala sharks and iridescent shark catfish (none are actual sharks of course, they just look similar). Unfortunately, none of them would be appropriate for such a small tank,
Becky on December 23, 2018:
Is there a type of fresh water fish that looks like a shark that can stay in a 5 gallon aquarium ?
Eric Dockett (author) from USA on August 04, 2018:
@cucu - My advice is 5 gallons and up. That is still a pretty small aquarium.
cucu on August 03, 2018:
anything smaller than a 1 gallon tank?
venus on January 30, 2018:
thank you for this article i am planing for next year to make a big aquarium
Eric Dockett (author) from USA on December 21, 2017:
@ME - While I'd much rather see a fish in a 10-gallon tank or larger, the fish listed above can do fine with the proper heat and filtration and correct tank maintenance procedures.
bella on September 21, 2017:
no bettas need at least a 3 gallon tank
Jack on November 26, 2016:
Great tips here! I like how you include information on how to actually care for fish instead of just listing off 5 good species for small tanks. My only gripe is that frogs and shrimp are technically not fish, but that's just me. I'm keeping a male betta by himself in a 10 gallon currently. I may see to acquiring a snail to help clear away some of the algae that's staring to grow on my plants.
Amelia on April 10, 2016:
Thanks! My 10 gallon holds a balloon molly, 3 neon tetra's, a male dwarf gremoe, and a black mystery snail.
Eric Dockett (author) from USA on December 09, 2014:
Thanks Aiden. Happy birthday to your Betta fish! Nine years is pretty impressive!
Aiden on December 08, 2014:
Great article. I'm partial to bettas. I have two now that are really old. The oldest will be 9 years old next week (December 14, 2014) and he was a fry I kept from my very first breeding of bettas. The younger one is only 4. I've stopped breeding them, but they're fantastic fish and well suited to the setup most people can provide.
sheilamyers on December 31, 2013:
Thanks for answering my questions.
Eric Dockett (author) from USA on December 31, 2013:
Thanks Turtledog, Dreamhowl and AliciaC.
Linda Crampton from British Columbia, Canada on December 30, 2013:
Thanks for this useful information. I haven't kept fish since childhood, but I would like to get some more at some point. Like all my pets, I would want them to be safe and happy, so I appreciate the advice in your hub.
Jessica Peri from United States on December 30, 2013:
I used to have a betta that I kept in a half gallon tank with a heater and small filter. Though the filter wasn't necessary I think he liked having warm water - he lived for two years of my college education. They are so much hardier than goldfish and much cleaner!
TurtleDog on December 30, 2013:
Thanks for the tips. With your help (and luck) nothing will die in my tank now . Voted up
Eric Dockett (author) from USA on December 30, 2013:
Thanks Sheila! It is generally true that larger aquariums require less maintenance. This is because smaller volumes of water pollute quicker. Fish waste and uneaten food lead to the buildup of toxic chemicals in the water, and the water must be changed frequently to keep it safe and healthy. Even one little fish in a three-gallon tank will pollute the water within a week or so. Big tanks have this problem too, but they are better able to cope with the build up of waste as long as proper stocking, feeding and monthly maintenance practices are followed.
Little tanks under 10 gallons are just so hard to maintain because its entirely up to you to keep the water clean. It's a constant balancing act, and very stressful for the fish. Big tanks can evolve into healthy little systems that almost take care of themselves, especially if there are live plants in there.
sheilamyers on December 30, 2013:
Great advice! Now I have a question for our resident aquarium expert. I've heard this so many times and still can't figure just how true it might be. Do larger aquariums require less maintenance? Or does it mostly depend on the type of fish you keep?
Eric Dockett (author) from USA on December 30, 2013:
Thanks Geekdom and My Cook Book!
Geekdom on December 29, 2013:
Perfect timing for this hub. We are looking to downgrade our tank to make more space in our place.
Dil Vil from India on December 29, 2013:
Well written hub, good work...