How to Care for Glofish Shark?

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Glofish sharks are a very popular breed of aquarium fish. They’re not sharks, technically speaking. It’s a genetically-engineered species of fish that comes in four colors. That’s why it’s called a glofish – because it glows. Their glowing body color makes them incredibly popular with children and not only.

But before you get a few glowfish sharks, you should know how to care for them. They have special needs and traits that make them more suitable for certain environments. Fortunately, they’re also very adaptable and resilient to environmental changes. Read below to find out how to care for glofish sharks!

What Is a Glofish Shark?

Contrary to its name, the glofish shark isn’t an actual shark. This is a genetically-modified strain of rainbow shark (Epalzeorhynchos frenatum), which is a species of egg-laying freshwater fish. The glofish shark was created and trademarked by Yorktown Technologies, L.P.

This glofish species comes in four colors. You can choose from cosmic blue, electric green, galactic purple, and sunburst orange. This strain is created through a technique called “transgenic insertion”. This means that when the sharks are still in the embryo stage, they receive an injection of fluorescent protein genes.

These genes get incorporated into the shark’s genome and are later expressed through a new trait— namely, a glowing body color. What this all means is that the glofish shark is basically just a fluorescent-dyed rainbow shark. Besides its bright colors and fancy glow, it looks and behaves exactly like a regular rainbow shark. It has the same body shape and size, temperament, water parameters, and so on.

How Long Do Glofish Sharks Live?

The life expectancy of a glofish shark is 4-8 years, the same as with the rainbow shark. Glofish sharks don’t exist in the wild, but their rainbow shark counterparts do. Out there, this fish species lives up to 8 years. When kept in captivity, both strains of sharks live less, around 4-6 years.

It takes diligent effort to bring a shark to the ripe old age of 6 though. This species is vulnerable to sudden spikes in water parameters. They need to be kept in top conditions at all times. This is part of what makes them a bit difficult for beginners.

Sharks are also predisposed to certain health issues that can shorten their lifespan. The most common potential health issues that can arise include bloat and constipation, dropsy, and ich. These problems can be fully treated if caught early. Otherwise, they become life-threatening.

How Big Do Glofish Sharks Grow?

In the wild, sharks grow up to 6 inches long. The average size of a young glofish shark (like the ones you’d find in stores) is 1-2 inches. When kept in captivity, sharks reach at least 4 inches in length. Fully-grown adult sharks aren’t any smaller than that.

Once they reach sexual maturity, you can expect your glofish sharks to go over 4 inches in length. And they grow quickly, especially during their first year. During a growth spurt, the young fish might even grow 1 inch per month.

There’s no strong sexual dimorphism in this species when it comes to size. Male and female sharks are virtually the same length. However, males appear thinner. Females have wider bodies because they need extra room to carry eggs for breeding.

Are Glofish Sharks Aggressive?

Sadly, glofish sharks are a semi-aggressive species. Adult sharks will chase, bite, and otherwise intimidate any other fish that crosses their path in the aquarium. They’re even aggressive with each other. In fact, sharks are so hostile that it’s nearly impossible to breed them in captivity.

Most of the aggression stems from their territorial tendencies. Sharks are loners and they like claiming spaces as their own. When other fish don’t get the memo, they’re in for a rude awakening. So, they don’t make great tankmates, that’s for sure. But you can still keep sharks with other fish. You just have to know how to choose them.

Sharks are bottom-dwellers and they’ll want the entire aquarium floor for themselves. So, pick middle and upper-level swimming fish as tankmates. Also, look for fish with a similar temperament. You’ll need stronger, more aggressive fish that can stand up against the bully sharks. I recommend fish like danios, gouramis, cichlids, loaches, and rasboras.

What is the Best Tank Size for Glofish Sharks?

Glofish sharks aren’t sociable, so they need a lot of space for themselves. You’ll need 50 gallons worth of tank space for each glofish shark you keep. This might sound unbelievable for new shark enthusiasts, but it’s true. A 100-gallon tank is an absolute minimum for just one pair of glofish sharks.

Remember, sharks are highly territorial. They also grow quite large at 4-6 inches in length. And they’re high-energy, fast swimmers. Not a good recipe for small community tanks. And the dimensions of the aquarium are equally important. Since sharks are bottom-dwelling fish, the tank floor must be long and wide enough.

An aquarium length of 48 inches or higher is a good approximation. Finally, even with plenty of size, you’ll have to add some decorations and hiding spaces. These help a lot, especially if you want to keep a pair of sharks. The decor offers additional spatial cues. This will help the fish separate their territories.

Do Glofish Sharks Need Filtration?

They absolutely do! And that’s due to three reasons. Firstly, you want the aquarium water to be as clean as possible. Any sudden spike in ammonia can be harmful to sharks. Second, sharks naturally prefer fast-moving waters like flowing rivers. And third, a good filter also ensures the water is always oxygen-rich, perfect for glofish sharks.

Using a high-quality filtration system can help you achieve all of these things effortlessly. However, you need to choose the filter carefully. Since sharks require a large aquarium, you’ll need a high-performance filter that can keep up with the demands. For glofish sharks, I recommend a filter with a flow rate 4-6 times the volume of your aquarium.

So, if you have a 50-gallon tank, you should choose a filter with a 200-300 GPH rating. If you also keep other fish in the aquarium, you might want to go for a higher GPH. Additional ways to increase the water movement include water pumps, air pumps, and air stones.

What Are the Ideal Water Parameters for Glofish Sharks?

The original rainbow shark is native to the quick-flowing rivers of Southeast Asia. You should emulate the shark’s natural environment as closely as possible. This means, first of all, warm water. The ideal temperature for rainbow sharks and glofish sharks is 75-80°F. Fish keepers in most climates need an aquarium heater to keep the water temperature within the ideal range year-round.

Sharks prefer neutral water. Anything between a slightly acidic to a slightly alkaline pH of 6.0-8.0 is safe. But for the best results, you should aim as close to a 7.0 pH as possible. The water should be soft to moderately hard. The optimal values are between 5-11 dGH. Nitrate levels should be below 20 ppm, while nitrites and ammonia should be 0 at all times.

Even a 2 ppm increase in ammonia or nitrites can cause stress and lead to health problems in glofish sharks. Sharks are very sensitive to sudden fluctuations in water quality. You need to ensure stable water parameters.

Temperature, pH, and ammonia are most prone to fluctuation. Investing in a heater and a filter can help you manage these factors. A small weekly water change (20-30%) is also necessary to keep the water clean.

What Do Glofish Sharks Eat?

Glofish sharks will eat anything. They’re an omnivorous species with a healthy appetite. However, remember that they’re bottom-dwelling fish. They prefer living and feeding at the bottom of the tank. So, foods that sink easily are the best choice for them. Apart from that, you can feed glofish sharks a variety of foods.

They need both protein and plants to maintain their beautiful glowing colors. Good protein sources include insects, insect larvae, and small crustaceans. Things like brine shrimp, daphnia, bloodworms, tubifex worms, and mosquito larvae make good choices. They’re also pretty easy to find in most pet stores. Live food or freeze-dried, anything goes.

This species is also a big algae eater. While it can’t survive on algae alone, a glofish shark won’t turn down good algae wafers. You can also feed them low-sugar vegetables like peas, zucchini, spinach, lettuce, Swiss chard, celery, and carrots.

Are Glofish Sharks Hardy?

Glofish sharks are quite hardy. They can adapt to various living conditions, as long as the transition is slow. They’re sensitive to fluctuations in water parameters, but this happens with every fish species. As long as there aren’t abrupt changes, your sharks will be fine.

Like all fish, improper care can lead to health issues. Things like bloating, dropsy, and ich can arise due to poor diet and water quality. Otherwise, this species doesn’t usually suffer from health problems. If you keep an eye on the water quality and the food, your sharks should be healthy and happy. There are even some perks to keeping glofish sharks.

Since you’ll be housing them in a large aquarium, you can expect the water parameters to be stable and easy to manage. The higher the water volume, the slower the buildup of ammonia and nitrites. This also leads to a slower decrease in pH.

Also, since sharks don’t school and they don’t like company, they’re highly unlikely to contact fungal or bacterial infections from other fish.


Caring for glofish sharks is a matter of patience, attention, and knowing the right things. These sharks are quite hardy and resilient, so you shouldn’t micro-manage their environmental conditions because they can adapt to many things. What’s more, these fish will eat almost anything because they’re omnivorous.

If you want to know more, leave a comment down below and I’ll reply as soon as possible!

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
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