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How Many GloFish In A 5 Gallon Tank?

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By Lindsey Stanton

yellow glofish in aquarium

GloFish are a relatively new species of fish, not a natural species, but a genetically engineered fish. As you might be able to guess, these little guys are genetically engineered to glow. This is especially true if they are kept under a fluorescent light.

The short answer is each GloFish requires around 3 gallons of water, but you shouldn’t really house them in a 5-gallon tank. They are schooling fish, so they like to be in groups (or schools) of 6 to 10. If you are planning on housing six GloFish, then get a 20-gallon tank. If you are planning on housing 10 GloFish, then get a 30—40 gallon tank.

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What Is a GloFish?

If you are wondering what a GloFish is, it is not a naturally occurring fish. At one point, these fish were Zebra Danios, but they have been genetically modified. Scientists added a fluorescent gene into these Zebra Danios to create these new and colorful GloFish.

As the name suggests, they do glow, especially in the dark. These little guys can come in many different colors from bright and fluorescent green and blue, to red, yellow, purple, and pink as well. Although these fish do not occur naturally, they have become very popular over the past years, especially with people who want killer display aquariums.

They also seem to be a prime choice for parents who have kids who would like fish. They are definitely quite fun to look at, plus they really are not all that hard to take care of either. On a side note, some Glofish originate from Tetra fish, but most come from Danios.

black tetra glofish (Gymnocorymbus ternetzi)
Image Credit: Grigorev Mikhail, Shutterstock

Glofish Minimum Tank Size

This is a bit of a difficult question to answer because the literature on these little fish is quite varied. These guys have not been around for very long, so different sources will tell you different things. However, we can give you our own best recommendation based on their size, temperament, and how they like to live.

How Many Glofish Per Gallon?

One single Glofish will grow to around 2 inches in length and they are schooling fish. Now, technically speaking, for one single Glofish, 3 gallons of water should be sufficient. However, these fish should not be kept alone.

A Word On 5 Gallon Tanks

In terms of a 5-gallon tank, you could technically house up to two Glofish but it’s not recommended. These are schooling fish and they like to be in groups of at least 6—10 fish. Therefore, if you want to keep six Glofish in a school, so they feel at home, the minimum tank size would be 20 gallons, ideally.

To really make them feel at home, you should keep them in schools of 10. For this, a 30–40 gallon+ tank would be best. The point here is that they technically do not need all that much room on their own, but they are schooling fish and should not be kept alone, therefore the spatial requirements for a school of Glofish are significantly larger.

Other Glofish Housing Requirements

In terms of keeping your Glofish at home in a nice aquarium, let’s quickly talk about some other requirements to keep these little fluorescent fish happy and healthy.

Glofish Water Temperature

To make sure your GloFish are healthy, a water temperature between 72 and 80 degrees Fahrenheit is required, and an average of 76 degrees is best.

glofish black tetra in aquarium
Image Credit: Aleron Val, Shutterstock

Water Acidity

Glofish are fairly hardy and resilient, so in terms of water acidity (the pH level), as long as you keep it between 6.5 and 8, they will be fine. Somewhere around 7.2 is best.

Water Hardness

In terms of water hardness, the dH level should be kept between 5 and 19, with a level of 11 or 12 being the very best.


The best thing to feed GloFish is any kind of high-quality tropical fish flake. You can feed them these twice per day, but most people choose to supplement something like brine shrimp once per day for some extra protein.


Glofish like to have a lot of leafy plants around, so get some Java ferns and Anubias for them to play around and hide under.


Glofish should get about 12 hours of light per day. They look best when you have white LED lights, and at night, they look best with gentle blue LED lights.

neon fish and jelly fish
Image Credit: Ievgenii Meyer, Shutterstock

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How many GloFish in a 10-gallon tank?

Seeing as a single GloFish requires 3 gallons of tank space to be comfortable, a 10-gallon fish tank could hold three GloFish.

As we mentioned above, they are schooling fish, so it’s strongly recommended to keep them in groups of six at a minimum, which requires a bigger tank (20 gallon+).

How many GloFish in a 20-gallon tank?

Seeing as a GloFish requires 3 gallons of space per fish, a 20-gallon aquarium could hold six GloFish comfortably.

What are the best tank mates for GloFish?

There are many good types of fish to house with GloFish, mainly other small and peaceful fish that will not pose a threat to them. Here are some of the best GloFish tank mates.

  • Guppies
  • Mollies
  • Platies
  • Swordtails
  • Barbs
  • Rainbows
  • Gouramis
  • Tetras
  • Loaches
  • Plecos
  • Corydoras

Do GloFish need special tanks?

There is nothing special you need to house GloFish. They do fine in a normal tank, just as long as it is large enough to house them comfortably, you have a good amount of light for the day, a good filter, some air, some plants, and decent substrate too.

What do GloFish need in their tank?

There is really not much you need for a GloFish tank. One thing we would recommend is to get dark plants and dark substrate, so the fish will really stand out in the dark.

Other than that you’ll need some basic smooth gravel substrate, a few plants, rocks, a good filter, an air stone, and LED lighting—all the usual basic requirements for aquarium fish.


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GloFish are really unique-looking fish that seem to continue to grow in popularity. Just keep them in a fairly large tank and keep them in schools, feed them right, get some lights, and all should be just fine.

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Featured Image Credit; Arunee Rodloy, Shutterstock

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