How Many Zebra Danios In A 20-Gallon Tank?

One can keep up to ten or twelve zebra danios in a 20-gallon tank. Zebra danios are naturally social fish and very active, so they require sufficient room to swim. If you wish to add other fish, you should reduce the number of zebra danios to no less than five fish.

Zebra danios are great fish to keep as they are so active that you can enjoy watching them zip about a tank. Being so active, they obviously require a well-sized tank to expend all that energy. 20-gallon tanks are a great size for zebra danios, but how many can you keep in a tank of that size?

How Many Zebra Danios In A 20-Gallon Tank?

If using a 20-gallon tank, you should not keep more than 10 or, at the very most, 12 zebra danios. This number will, however, change depending on other factors.

We will look at the various factors surrounding the number of zebra danio you can keep in a 20-gallon tank and provide you with everything you need to know about the maximum and minimum number of fish you can keep in such a tank.

Zebra Danio

How Many Zebra Danio Should Be Kept Together?

As far as fish go, zebra danios are some of the most pleasant and low-maintenance fish to keep. Zebra danios are social fish, and they are very busy, so they have lots of room.

As zebra danio grows to a size of a maximum of two inches, the smallest tank recommended for zebra danio is 10 gallons if one works on the concept of one inch of fish per 1 gallon. This is because zebra danio should not be kept in schools of less than five fish, and they can grow to a maximum length of two inches.

The fish per gallon rule is not exact but can be held to be fairly reliable for smaller fish like zebra danios. Applying this theory to a 20-gallon tank will allow a maximum of ten and possibly twelve zebra danios.

Determining The Number Of Zebra Danios In A 20-Gallon Tank

While we know that the maximum number of zebra danio in a 20-gallon tank is, some factors may impact this number, and these need to be taken into account.

  • Tank ornamentation and design
  • Tank foliage and plant life
  • Tank mates
  • Breeding

Tank Ornamentation And Design

This can surprisingly impact the number of fish you can keep; after all, these things do take up a lot of space. Ultimately one would design a tank based on the fish you are keeping, so with zebra danios, a tank with swimming space is a must.

When it comes to a 20-gallon tank, a longer design rather than a taller one is recommended; this will allow the maximum number of zebra danio. If you opt for a shorter but taller tank, then rather reduce the number of zebra danio down to five or six.

If you like lots of ornaments for fish to use as shelters, ensure that there is still enough swimming space or, again, reduce the number of fish kept.

Fortunately, zebra danios swim in the tank’s upper parts.

Tank Foliage And Plant Life

Some fish like many plants as they hide in the leaves and fronds. Zebra danios like plants but don’t need them to be thickly planted as the fish like to swim and need space as they prefer the upper regions of the tank.

If you wish to keep the maximum number of zebra danios for a 20-gallon tank, you should ensure that your plants are not too numerous but just enough to keep your fish happy.

If you really like tank plants, then reduce the number of zebra danios to five or size to allow for a few more plants. Always be sure to allow your fish sufficient swimming area so they can thrive.

You may also get away with a few more plants, provided they are lower-living plants.

Tank Mates

Zebra danios are known to be easy and relatively peaceful fish. They are often kept with other species due to their friendly temperament. With a 20-gallon tank, there is sufficient room to keep more than just zebra danios.

Zebra danios live well with other small species, provided they are not too small and can handle the energetic pace of the zebra danios. One can easily keep six to eight zebra danios with other similarly behaved species, provided you keep to the fish per gallon rule.


Zebra danios are known to be good breeders, so don’t be surprised if you suddenly find yourself with a lot more fish than you started with. In these cases, it is recommended to invest in a breeding tank, as your 20-gallon tank may soon be overrun with fish.

Best Fish To Keep With Zebra Danios In A 20-Gallon Tank

If you are looking to keep other species with your zebra danios in a 20-gallon tank, we have put together a list of our top five picks of compatible species and provide you with the recommended number of zebra danios that can be kept alongside them. Fortunately, zebra danios are considered to be good tank mates.

  • Neon tetra – these are also energetic small fish, and you can keep eight zebra danios and a school of ten neon tetra.
  • Honey Gourami are slightly larger fish and make good tank companions for zebra danios; you can keep six zebra danios with two honey gourami.
  • Cherry Barbs – these are lovely vibrant fish and look good alongside zebra danios; you can keep six zebra danios and six cherry barbs together in a 20-gallon tank.
  • Cory catfish – you can keep four to six cory catfish with five or six zebra danios.
  • Platies – you can keep up to six platies with six zebra danios.

Many more species are compatible with zebra danios; always check that the other species have a similar temperature as well as the same environmental requirements.


If you want to keep zebra danio, you can keep up to twelve fish in a 20-gallon tank. The minimum number you should keep is five.

Zebra danios are busy fish and need areas to swim in. They can be kept alongside other species with similar temperaments; however, the number of zebra danio may need to decrease to ensure enough room.