Best Fishes for Small Tanks

Finding space for a fish tank can be difficult. You might be picturing one in your office or apartment but feel uncertain about the commitment to a huge aquarium. The good news is there are plenty of small tank options to take advantage of. There are also lots of adorable fish to fill the tank with.

Quick Answer

Small tanks range from 2.5-gallon to 15-gallon options.

The best tropical fishes for a small tank are Rasboras (Dwarf or Chili), Tetras (Ember or Bloodfin), Endler’s Livebearer, Betta Fish, and Guppies.

For a coldwater-only aquarium, though, White Cloud Minnows and Panda Corydoras are the best choices.

Some fishes can handle cooler or warmer temperatures, like the Pearl Danio, Zebra Danio, Neon Tetra, and Platy.


Best Tropical Fish For a Small Tank

If you prefer the tropical route over the coldwater route, you’ll have plenty of fish to choose from. Here are some of the best ones:

Rasboras (Emerald Dwarf Rasboras or Chili Rasboras)

These species are shy, but they love to move. A 10-gallon tank will be better for these active swimmers. They need a pH between 7-8 and water between 70-75? for Emerald Rasboras and 70-80? for Chili Rasboras. As long as they have their school and hiding places, they’ll be happy.

Tetras (Ember Tetras or Bloodfin Tetras)

A school of tetras in your tank will add color and take up minimal space. These fish are tiny but more social. You’ll want a higher temperature–between 78-82?–but a lower pH–about 6. This pH means they’re not very compatible with Guppies or Endlers, but 6-8 tetras with other peaceful fish will make a vibrant tank.

Endler’s Livebearer

Endler’s Livebearers like it warmer–78-80?–but they keep it cool. These fish get along well with their own kind and other species. The “livebearer” part is true, though, so having more males than females can prevent overbreeding. They like a 7-8.5 pH level, so make sure your other fishes can handle that. Schools should be around 4-5 at least.

Betta Fish

Betta fish are popular choices for their adaptability and beauty. For a small tank, though, it’s best to keep one male betta fish by himself to avoid aggression, and keep your water  between 78-80?.


Guppies are small, colorful additions. Keep them in a 5-gallon tank (or larger) with up to 6 fellow guppies, but only keep one gender to avoid constant breeding. Water temperature should be between 75-82? with a neutral pH.

Best Coldwater Fish for a Small Tank

While tropical fish are popular, many aquarium hobbyists prefer a nice coldwater aquarium. When it comes to temperature, some fish can handle the cooler waters known to “coldwater” fish.

What’s important when combining adaptable tropical fish, like the first four below, with coldwater fish, like the last two, is maintaining a temperature that falls within all of their ranges.

Pearl Danio

Pearl Danios are tropical, but they can handle a range of temperatures, from about 65-78?. Keep the pH neutral with these. They’re on the shy side, so plants are a must, but they’ll feel comfortable with Endler’s Livebearers or Bettas.

Zebra Danio

Our second tropical fish here, Zebra Danios, have a slightly smaller temperature range than their Pearl counterparts at 65-75?. They’re schooling fish, so keep at least 5 together. Beginners will find these easy to care for.

Neon Tetra

Neon Tetras are one of the most popular fish for hobbyists. They’re also tropical and need a slightly warmer temperature than the ones above, around 68-78?. You can pair them with a hardy coldwater fish, though, like a White Cloud Minnow. Just balance the temperatures and pH levels out by keeping the water from 68-72? and the pH between 6-7. Keep these with at least 6 other Neon Tetras and you’ll be set.


The last tropical fish that can handle colder temperatures to consider is the Platy. These fish like their water between 68-82?, so they can be paired with some of our tropical picks, too. Their preferred pH is between 6.8-8, though, so only pair these with fish that like harder water. Platies do school, but in smaller groups around 5.

White Cloud Minnows

Moving onto the true coldwater fish, White Cloud Minnows are easygoing and simple to care for. While you can keep a school of them in a 5-gallon tank, they’ll live longer and be happier in a 10-gallon. The best temperature for them is 64-72?, with a pH between 6-8. Be sure to keep at least 5 others and they’ll be very social.

Panda Corydoras

The Panda Corydora is a perfect choice for a 10-gallon tank. While their adult length can get to 2 inches, beyond the small-tank recommendation, most don’t get this long. They like a pH of 6-7 and a temperature between 68-77?. The right Tetra or Rasbora will pair well with this species, but school with no less than 4.

Choosing The Right Tank

A small tank is any tank that holds 10 gallons or less of water. Most tanks come in the standard rectangular shape and these are better than different-shaped ones.

Most of the tanks you see fall under one of three categories: show tanks, long tanks, and regular tanks. Show tanks are self-explanatory, as they’re typically used in aquarium shows by professional hobbyists. Long tanks are shallower than show tanks but wider. They need a bigger area for set-up.

The regular tank category covers the rest of the tanks you’d see sold in pet shops. Another distinction to keep in mind is tall versus long tanks. The main difference between these, and a key factor when choosing one, is the water’s surface area.

Long tanks have more surface area than both tall and show tanks. This is where carbon dioxide and oxygen exchange, so it’s crucial for your fishes’ health. If you’re debating between more surface area or more gallons, prioritize surface area.

There is some debate among enthusiasts about whether someone should choose a tank first or fish first. Because small tanks only offer a limited species of fish to choose from, choosing a tank first is okay.

If your heart is set on a specific breed, however, do the research on their tank requirements beforehand. Look at the water temperatures and pH levels required. Small fish will probably also need sponge filters, as other filtration can suck them in.

Another factor to consider is how difficult it will be to maintain. Unless you’re a professional, a bigger tank will put less stress on you and your fish. Even choosing a 10-gallon over a 5-gallon can make the water parameters more stable–meaning fewer water changes and cleanings.

Once you have your tank, you’ll also need proper equipment, like a filter and heater. If you’re looking for easier maintenance and set-up, look at small tanks that come with built-in filters and heaters. You can also get a kit that matches the requirements of the fish you’re looking into.

You have your tank and it’s time to fill it with fish, but how many?

How Many Fish Should You Have?

The number of fish to stock in a small tank depends on their temperament, adult lengths, and food preferences.

Other factors to consider are whether you have room for plants and hiding spots, what type of filtration the breeds require, and how much experience you have.

The Temperament of the Fish

Some fish are more aggressive than others. The Betta fish, for example, is known as the “Siamese fighting fish” for a reason. For a small tank, aggressive fish can get territorial. If you want a fish with this temperament, it’s best to keep them by themselves.

Another factor is whether the breed schools or not. Schooling fish need to be with a certain number of their own kind to feel safe. The exact number depends on the breed.

Adult Lengths

Whether you buy a fry fish or an adult fish, the tank you put it in needs to fit its adult length from the start. For a small tank, each fish should stay around 1 inch in length. One important tip here is to not choose goldfish for a small tank. It seems like a normal practice, but goldfish’s adult length gets between 10-12 inches and they will suffer in a small tank.

Type of Food

When choosing the number of fish and whether you’ll be mixing breeds or not, choosing fish that eat high-quality food will help you keep your tank clean. Certain foods like cheaply-made flakes will taint the water more quickly over time, meaning more water changes. Water changes put stress on your fish, too, so minimize them by choosing fish, or groups of fishes, that eat pellets or freeze-dried food.

Plants & Hiding Spots

Some fish, like people, are just shy by nature. These fish will need hiding spots in the form of rocks, plants, or driftwood, to name a few options. Otherwise, they may hide behind the tank’s equipment and this can be dangerous. However, this will factor into the number of fish you have, as more items in the tank mean less room overall.

Experience Level

If you’re a beginner, you may want to have as many fish as possible. While it’s great to be excited, keeping fewer fishes until you’re confident in your knowledge and abilities for caretaking can give your fish better, longer lives.

With this in mind, you’re ready for the final step: choosing fishes.


Now that you know how to pick the right tank–with plenty of surface area–and the best fish, you’re probably revved up to start your first aquarium. Or maybe you have experience and are looking to add a small tank to your collection. Did any of these tips surprise you? Is your mind made up or are you debating between a few? Let us know in the comments!

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