How Many Glofish in a 10 Gallon Tank?

Glowfish Tetra

Whether you are a hobbyist or diehard fish lover, having an aquarium full of brightly colored fish and plants is a dream. No wonder so many people want to add the aesthetically-pleasing glofish to their tanks. After all, nothing is more exciting than to watch a rainbow-bright school of fish flash from one end of the aquarium to the other as their bodies glow throughout the night.

But if you find yourself wondering about how many glofish per gallon or how many glofish in a 10 gallon tank, you are not alone. Many people have been confused by this in the past, which is why we wrote this article!

Keep reading to get answers to your questions about how many glofish to keep in a 10 gallon tank and why.

About Glofish

Although bioluminescence is a naturally occurring phenomenon in many living organisms, it was, for a long time, not something you saw in aquarium fish. The ability for animals to produce a natural light is more than cosmetic, of course. 

In the wild, vampire squids can eject luminescent mucus to frighten off predators, and there are even species of worms, plankton, and coral that can emit light to either attract prey or scare off anything hunting them.

Singaporean scientists were the first to genetically modify common fish to make them fluoresce. The idea was using the bioluminescence as a way to detect whether certain types of toxins were present in waterways so that communities could be advised.

Once that was a success, a Texas-based company called Yorktown Technologies purchased rights to the research and later introduced the first aquarium glofish—the Starfire Red Danio—to the market in 2003.

These days, there are multiple types of glofish, including glowing tetras, danio, barbs, and zebrafish, in a number of colors, including pink, blue, and green. Though the fish do not appear to be glowing all the time, they will brightly fluoresce in the presence of blue light or black light.

For those who are concerned or who have heard myths about how glofish are created, it should be known that these fish are bred to glow. They are not injected with neon or with color after birth. 

The gene is injected into each fish embryo, one at a time, allowing for the fluorescence to eventually be passed down through the generations. That is why you should purchase glofish from reputable sellers, because you know for sure they have been bred—not dyed—and are healthy.

Glofish Species, Tank Mates, And Growth

As Mentioned Earlier, There Are Different Kinds Of Glofish. Because Of This, Not All Glofish Are Going To Mix Well With Other Fish. To Understand The Various Species And How Well They Mingle, Here Is A List Of Common Glofish Species:

Glowfish Tetra

Glofish Tetras

Peaceful Schooling Fish That Can Have Numerous Tank Mates And Do Not Require Much Swimming Space. Tetras Grow To About 6.35 Cm (2.5 In) Maximum. Ideal Tank Mates Include Angelfish, Barbs, Betta, Danio, Other Tetras, Minnows, Guppies, Rasbora, Cory Cats, Killifish, And Swordtails.

Glowfish danio

Glofish Danio

The most common species of glofish available, the danio is small and grows to about 6.35 cm (2.5 in). Sociable and compatible with the great variety of fish, they are ideal for tanks with plenty of swimming space for darting around. Ideal tank mates are similar to tetras and include angelfish, platy, pleco, rasbora, swordtail, loach, molly, hatchet, discus fish, barb, betta, tetras, and minnows.

glofish tiger barb

Glofish Tiger Barbs

Known to be slightly aggressive, tiger barbs enjoy schooling among themselves but will become feisty when it comes to other tank mates. In fact, they may nip at smaller fish, even though they only grow to about 7.6 cm (3 inches) in length. The best tank mates for tiger barbs are barbs, cory cats, danio, gourami, guppies, loach, molly, minnows, pleco, rainbowfish, rasbora, and tetras.

glowfish rainbow shark

Glofish Rainbow Sharks

One of the newer additions of glofish, the rainbow shark is also semi-aggressive. They are bottom feeders who spend most of their time amid the substrate. Since rainbow sharks can grow to about 24 cm (6 in) in length, they are not recommended for 10 gallon tanks or smaller. These fish are also not very compatible with other tank mates but will tolerate barbs, danio, minnows, rainbow fish, and gourami. Exercise extreme caution when introducing other sharks.

Caring for Your Glofish

Taking care of glofish is like taking care of their non-glowing counterparts. This means that temperature preferences, life expectancy, and growth rates remain the same. On average, the lifespan of a glofish is anywhere from 3.5-5 years.

Depending on the species of glofish you have, the conditions of the tank may be different, but the following is considered ideal for most breeds:

72-82 degrees. You will need an aquarium water heater to keep the temperature constant.
pH Levels
Anywhere between 6.0 - 7.0 pH
Also, keep in mind that glofish tend to like glowing. This means you also need to give them a source of light that allows this to happen. Blue light is preferable to these fish, because it allows them to shine bright. Be sure to purchase some blue light decorations and gravel. This keeps your fish satisfied while providing the aesthetic you want.

Now that you know more about glofish varieties and how to care for glofish, it is time to answer questions about how much space and how many glofish in a 10 gallon tank are considered ideal.

Glofish Per Gallon: A Breakdown

Keeping the information about growth, temperature, and tank mates in mind, you can now start thinking about the size tank you want to house your glofish. The main thing to understand is that these are schooling fish—aside from the sharks. This means they need space.

5 gallon tanks are not recommended at all for glofish, no matter how small they are. That is why a 10 gallon tank is considered the bare minimum for owning glofish. However, a 10 gallon tank can quickly become too overcrowded when you have a lot of decorations. Ensure you have struck a balance with swim space and hiding space in your tank to keep your fish happy and healthy.

Here is a breakdown per gallon:

  • 5 Gallon Tank: Not advised. Leads to aggression and poor health.
  • 10 Gallon Tank: Ideal for a single school of danio and tetra (about 5-6 fish). Not recommended for tiger barbs or rainbow sharks.
  • 20 Gallon Tank: 5-6 fish. The bare minimum for tiger barbs and rainbow sharks.
  • 30 Gallon Tank: 9 fish.
  • 50 Gallon Tank: Can provide ample space for more than 10 fish.

Because danio and tetra fish grow to a maximum of 2.5 inches, 10 gallon tanks are considered perfect for them. However, this is only if you are keeping a school of glofish danio or tetra and nothing else. Tank mates are not recommended if all you have is a 10 gallon tank.

How is this calculated?

“How do you know only 5-6 fish can fit in a 10 gallon tank?” If you want to figure out the approximate amount, you need to use a little arithmetic. First, consider the maximum length of the fish you wish to add to your 10 gallon aquarium. Neon tetra, for example, reach a maximum of 6.35 centimeters (2.5 inches) but rarely grow beyond 5 cm (2 inches).

However, in terms of sizing, you should always overestimate the growth of your fish. If you use too small a number, you may end up with a small, overcrowded tank—and no one wants that. So, for example, if you want to add some glofish danio, which usually grow to about 4.5 cm (1.8 inches), you might round up to 5 cm (2 in).

A general rule of thumb is that for any fish under 7.6 cm (3 inches), they will require about 1 gallon of water per fish. Therefore, a glofish tetra that is 4.45 cm (1.75 in), needs about 1.75 gallons. Easy, right? So, in terms of a 10 gallon tank, you would simply divide 10 gallons by 1.75 inches, leading to 5.7, which brings us to 5-6 fish in a 10 gallon tank.

Now, this is where the size estimate comes in handy. If your fish are smaller than average, you might be able to squeeze in a seventh. But that would be pushing it.

Can I Keep A Betta With My Glofish?

A popular trend is for people to buy a single betta fish and pair it up with glofish danio or tetras, since bettas can get along with tetras and danio rather swimmingly (pun intended). However, if you decide to introduce a betta to a 10 gallon tank with glofish, you are going to have to make adjustments for how fish go inside.

A betta fish will require about 3-5 gallons of water to be happy, with 5 gallons being ideal. If a betta has 5 gallons to itself, there will be no aggression and no fights. That leaves 5 gallons for your small glofish to thrive. Remember what was said before? That’s not really the best set up.

In other words, you could only fit about 2-3 glofish tetras in a 10 gallon tank with a betta fish, and you might want to skip the danio altogether.


Glofish are colorful additions to any aquarium and are bound to liven up your home. They are excellent fish for beginners and tend to mix well with other fish. If you are planning on getting a 10 gallon tank to house glofish, keep in mind that only neon tetras and glofish danio are recommended—and that only 5-6 fish can happily live in that size aquarium.

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