Don’t judge a fish by its tank. Nano tank fish have some of the biggest and baddest attitudes in the underwater world. They might not know how little they are in the grand scheme of seas, but you’ll without a doubt start to see them for what they really are — beautiful, fun, intriguing … and relatively simple to care for.
Nano tanks are some of the most popular choices in aquariums, and it’s easy to see why. They don’t require as much space. They don’t cost as much as a massive tank for larger fish, and the options for beautiful nano tank fish are abundant.
9 of the Most Popular Nano Tank Fish
A nano tank is defined as a tank that is 20 gallons or less. Its size, however, doesn’t stop hobbyists and aquarium maintenance technicians from designing an aesthetically pleasing ecosystem complete with gravel, plants, and decor.
Following are some of the most popular fish for nano tanks, and why that may be so.

1. Harlequin Rasboras & Chili Rasboras
What can we say? Chili rasboras and other rasbora species are some of the hottest nano tank fish for many reasons. In fact, there’s really nothing not to love. They’re vibrant in appearance and personality. They’re fun to watch. They don’t grow larger than about an inch. They’re gentle and peaceful, and, best of all, they are some of the easiest pet fish to care for in general. You could keep two rasboras in one gallon of water, but that’s no fun. Go for as much as 20 gallons to really see them shine.

2. Neon Tetras
The name says it all. “Neon” goes with an aquarium like “fresh” goes with water. At least 2 gallons of water per tetra is ideal.

3. Betta Fish/Fighting Fish
We could admire these little guys all day. Known by their characteristic flowing tails and fancy fins, they’re as tough as they are glorious. But don’t believe what you see in the supermarket; a tiny cup of water for them to live in simply won’t do. A 5-gallon tank or larger is recommended.

4. Guppies
Guppies are available in a wide variety of colors, and they can do just fine in a tank that is as little as 5 gallons. You might want to choose male fish only for a nano tank, however, because guppies reproduce like rabbits. … Well, more than rabbits, but you get the picture.
5. Minnows
Certain species of minnows are colorful, cold water fish that don’t even require a heater. Four or five pairs of minnows can fit into a 15 gallon tank.

6. Zebra Danios & Celestial Pearl Danios
The word “pearl” may be a reference to the elegant spots on their bodies, and likewise, the word “zebra” refers to the mesmerizing horizontal stripes. Although they only grow to about an inch long, pearl danios require a tank that is at least 10 gallons while zebra danios need a 15 gallon tank. A true nano tank can hold up to 20, so you’re good.
7. Sparkling Gourami
These fish look like their floating on air … err, water. That’s part of the reason why they are among the most popular nano tank fish. They’re also very peaceful and like to swim up to the surface, which can add a spark of character to your aquarium. They grow to about 1.5 inches and also require a 15-gallon tank.
Maintaining a Nano Aquarium
Although the fish themselves aren’t very demanding, keeping a nano tank clean can be a bit of a challenge. Because the tanks are so small, you’ll need to be extra vigilant.
- Make sure water changes are completed regularly and on time. That water can become murky faster than you can say “nano”.
- As with any fish, don’t overfeed them. That’s especially important when the waste can collect easily.
- Maintain the proper pH level and temperature at all times. Such a small environment can heat up quickly. The pH level depends on the type of nano tank fish you have, as well as whether it is a freshwater or saltwater aquarium. Let us know what kind of fish you have or want, and we’ll let you know the general recommendations.
- Keep the decor clean for the same reasons. If you have algae-covered artificial decor in the tank, remove the items and place them in the sun for a few days. After the algae dries, you should be able to wipe them right off and replace them. When you do clean the decor, move the livestock to a temporary tank until you can freshen up the main aquarium.
If you think maintaining a nano fish tank will be rather time consuming, that’s what we are here for! Our aquarium maintenance company in Phoenix, Arizona will keep that aquarium clean and beautiful for you, allowing you to sit back and enjoy the lively characters that live inside.