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What are the Best Fish FoR 20 Gallon Tank

If you’re interested in becoming a fish owner, you’ve probably done a lot of research into what the right size tank would be. A lot of factors have gone into this: you want a tank that’s both easy to maintain and has enough room for a school of fish made up of many types, and you also want to stay within your budget while still being able to safely care for any fish you end up housing. 

And throughout all of this research, you’ve come to the rightful conclusion that you need a 20 gallon tank!

However, now you need to move onto the next step: what fish would be best to keep in this 20 gallon tank?

To help you on your journey to becoming a fish-keeper, we’ve listed 6 of the most common and popular species below that would suit your tank set-up the best. 

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Top 3 Mistakes Newbies Make Setting Up Their Fish Tank.


 The Best Fish For 20 Gallon Tank

If you’ve already picked the perfect tank, now’s the time to fill it with healthy and happy fish!

Here’s our list of the best fish for a 20 gallon tank, with more information below on the best combinations to keep as well. 


Blue Neon TetrasBlue Neon Tetras

Small fish that like to hide, Tetras are great for a 20 gallon tank. Neon Tetras are the most popular type, thanks to their iridescent scales and easy recognisability. They’re schooling fish, so they will need to be kept with at least 4 - 8 other neon tetra fish.


Red GuppyRed Guppy

Being quite simple to care for, and as one of the most colorful fish we know of, Guppies are a popular pick for a 20 gallon tank.

They get along well with most other species, and work well as part of a communal tank you’re putting together. They’re small and agile swimmers, and need to be kept in a small school to save any from being singled out by much bigger fish.


Corydoras CatfishCorydoras Catfish

There are many species of Catfish, but the species within the Cory Catfish genus work best for a 20 gallon tank.

Being bottom feeders, they’re quite peaceful, and will help to clean the tank. Cory Catfish are best kept in a small shoal of at least 6, but a 20 gallon fish tank will typically not allow for many more than this.


Rainbow PlatyRainbow Platy

Small in shape and one of the fastest swimmers on this list, Platy fish are a great addition to a 20 gallon tank.

You’ll have to keep them with other platys - however, they’re not your typical schooling fish. It’s best to have 2-3 females for every male if you keep multiples of them. 


Amano ShrimpAmano Shrimp

A big community fish, Shrimps are small and great for easygoing 20 gallon tanks. Great for keeping alongside other small and peaceful fish, Shrimps will add a bit of dimension to any tank you keep.

The Amano Shrimp is one of the most popular type you can find, and will scavenge in a similar manner to Corydoras Catfish.


Coloured CichlidColoured Cichlid

A non-schooling fish, and potentially aggressive in nature, Dwarf Cichlids are an appropriate species of Cichlid to keep in your 20 gallon tank.

Other species, such as the African Cichlid, are too big to fit healthily into such a space. Be sure to introduce a simple mated pair to the tank at this size; if you introduce any more Cichlids, it may lead to fighting over territory. 

What Fish are Best To Keep Together

  • From the list above, there are a few safe combinations for your new 20 gallon tank

  • Catfish, Guppy, Platy, and Tetra species all work and play well together, so they’re a very safe combination if you’re looking to house as many fish as possible. 
  • Similarly, Catfish, Tetra, and Cichlids are also good for keeping in the same tank, but refrain from adding any Guppies to this combination.

  • Shrimps and Guppies also live well together; they’re both small and docile species, meaning they won’t bully or attempt to feed on each other when housed together.

  • Note: It’s a good idea to think about species that typically school when thinking about homing multiple species. At least 4 fish need to be in a school together, and they’ll always prefer to be housed with other fish of their own kind. Keep in mind your capacity needs if adopting any fish that tend to group together if you want 2 or 3 different types of fish to care for.