Glofish Shark Care Guide | Diet, Habitat, Breeding, Accessories

Jan 21, 2022

Glofish Shark Care Guide

Glofish sharks are stunning to look at. They’re also hardy enough to thrive in a wide range of water conditions. But they’re not suited for everyone. 

Why? They have a notorious temper. 

If you are a beginner, we suggest keeping your distance from glofish sharks for a couple of years until you get the hang of dealing with aggressive fish. 

And if you have already brought glofish sharks home, I’m sure this one-stop guide will prove helpful to look after them the right way. 

Glofish Shark Quick Introduction 

NameGlofish Shark
Original SpeciesRainbow Shark
FamilyCyprinidae 
Origin Captive-bred
Care Level Moderate
Temperament Aggressive
BreedingEgg-layer
Diet Omnivore
Maximum Size6 inches
Care LevelModerate
Minimum Tank Size50 gallons
Temperature24-27 degrees F (75-81 degrees C)
pH6-8

Here’s a bummer: Glofish sharks aren’t actually sharks.

As a matter of fact, they come from the minnow family and are more closely related to carps and loaches than great white sharks. 

But don’t get disheartened. A glofish shark’s persona and temperament are just as majestic and fierce as the real sharks’. 

Glofish sharks were introduced only in January 2018. And in just 4 years, their popularity has grown quite steeply! 

From what I see on forums and threads, it wouldn’t be wrong to say they have a cult following! 

Glofish sharks were created by genetically modifying rainbow sharks. 

The fluorescent protein extracted from various marine organisms like jellyfish was injected into the rainbow shark embryos, which resulted in their colorful and luminous appearance. 

Glofish sharks are simply beautiful, hardy, and of course, sassy at times. It sure is a treat to raise these beautiful fish. 

Glofish Shark Lifespan 

On average, glofish sharks live for around 4-6 years. But with the right care, they’re known to even make it to their 8th birthday. 

In an aquarium, how long glofish sharks live depends on the extent of care you provide and the kind of diet you give. 

Creating a stress-free environment, offering a well-rounded diet, and keeping the water quality pristine at all times will ensure your glofish shark leads the longest life possible. 

When Do Glofish Sharks Mature?

From my research, it seems there isn’t a specific age to answer when these fish mature. So we have to study from the size’s perspective. 

Glofish sharks typically reach sexual maturity once they grow around 4 inches in length. And this takes a good couple of months. 

Glofish Shark Appearance 

Glofish sharks look like miniature sharks. There’s no denying that. They aren’t remotely related to sharks – that’s a different thing. 

Glofish sharks have a very distinctive appearance. Long and slender bodies, a flat abdomen, pointed snouts, and raised fins make them uncannily look like sharks. 

Especially, the upright dorsal fin gives them the appearance of a shark. 

The fish has two eyes, one on either side of the head that often have a sunken appearance. 

The body is rounded near the head and the back and tapers off as it reaches the tail. 

And the linear area from the gill cover, the eyes, and the mouth have a characteristic brief stripe. However, it may be hard to notice in genetically modified glofish. 

Glofish Shark Colors 

Glofish sharks come in 5 beautiful colors: Cosmic Blue, Galactic Purple, Electric Green, And Sunburst Orange. All 4 of these colors are patented. 

My favorite color on glofish sharks is cosmic blue. The iridescent blue body coupled with a warm yellow head and fire red fins give the fish an otherworldly appearance. 

And none of the gossips about these fish being dyed, injected, or painted is true.

The first generation of rainbow sharks were genetically modified by inserting the fluorescent protein gene extracted from jellyfish and other marine organisms into rainbow shark embryos. 

Then, the fluorescent gene is carried from one generation to another through traditional breeding. 

Therefore, the colors don’t fade over time as it does in some other artificially dyed fish like jellybean cichlids and painted glassfish. 

Glofish Shark Size 

Glofish sharks grow around 6 inches long. But some prodigies are even known to reach 8 inches. 

6 or 8 inches, they’re the biggest and longest fish in the glofish family. And they need a sizable tank to accommodate their grand physique! 

More about that later! 

Glofish Shark Males VS Female

In glofish sharks, males sport a brighter and richer coloration than females. But this distinction is not seen in glofish sharks as both males and females look equally colorful. 

Nonetheless, females have a thicker and more rounded appearance. It’s even more apparent when they’re gravid. 

On the other hand, males are slender and slightly smaller. 

Males also have gray lines on their tail fins. But once again, this characteristic is barely noticeable in genetically modified glofish sharks! 

Also, as juveniles, it’s next to impossible to tell males and females apart. You can only know once they reach adulthood and the females start getting thicker-bodied. 

Glofish Shark Temperament 

In the wild, rainbow sharks are docile fish that keep to themselves and seldom attack anyone. However, this doesn’t hold true for their genetically modified variants aka glofish sharks. 

Frankly, sharks are as aggressive as they come. 

They are highly territorial fish with anger management problems. 

Therefore, if you’re a beginner, I’d strongly suggest against keeping glofish sharks. 

As glofish sharks are territorial, they’re very much likely to attack anyone if they feel their space is being encroached. And this is the number one reason why you should only have 1 rainbow shark per tank. 

However, when provided enough space, glofish sharks are well mannered for the most part. They’ll even get along with fish they don’t perceive as a threat. 

Glofish Shark Tankmates

Glofish sharks should be placed with semi-aggressive, similarly-sized fish that can hold their ground. 

Some ideal tankmates for glofish sharks would be:

  • Rasboras 
  • Loaches (Can be dicey)
  • Danios
  • Rainbowfish 
  • Gouramis 
  • Tetras

If you fail to add equally-aggressive species, there’s a good chance your glofish shark will bully them to the brink of death. 

Since these fish spend a good portion of their time at the base, you shouldn’t keep them alongside bottomfeeders like plecos and catfish. It will result in a bloodbath. 

Tankmates to avoid for glofish sharks:

  • Other glofish sharks
  • Rainbow sharks 
  • Red-tail sharks
  • Bala sharks
  • Catfish
  • Cichlids

Glofish Shark Ideal Group Size 

The rule of thumb is to keep just one glofish shark per tank. There are hardly any rules etched in stone in the aquarium hobby, but this is one of them. 

Glofish sharks simply do not tolerate living with other fish of their own kind. Socializing and cohabitating aren’t their thing. 

Even in the wild, their wild cousins – rainbow sharks – lead a solitary lifestyle and are highly territorial.

And this nasty trait has very well been passed on to glofish sharks. 

For instance, if you keep 2 of them together, the bigger and dominant one will chase and attack the subdued fellow until it succumbs to death. 

You may be able to house multiple glofish sharks as juveniles, but as they grow, their ballistic personalities grow too. 

And you’ll need to separate them to avoid any bloodbath in the tank. 

However, if you still insist on keeping more than 1 glofish shark in the same tank, I’d recommend keeping at least 5 or more. 

This way, the mean boss will have quite a few options to lash out at. The anger and bullying will be spread out. 

But you will need a super big tank to keep multiple of them. I’m talking 200 gallons or bigger. The bigger is always better.

Glofish Shark Diet 

Although glofish sharks look like avid predators, do you know their wild cousins primarily snack on algae in the wild? So, yes – glofish sharks are omnivores, too, with a great affinity for algae-based food. 

In the tank, they will readily feed on common fish food like pellets and flake food. And since they’re bottom feeders, you have to make sure the food you offer sinks to the bottom. 

Your shark will also love to occasionally snack on small crustaceans and insects. So you can give them a few times a week. 

And lastly, don’t forget to fortify their diet with some boiled vegetables. Yes, veggies – you heard them right! Your sharks will love them. 

Just make sure to cool before adding them to the tank. And remove leftovers immediately after they’re done eating as organic matters rot fast. 

Here’s a comprehensive list of food suitable for your glofish sharks:

  • Sinking pellets 
  • Flake food 
  • Algae tablets 
  • Algae wafers 
  • Bloodworms
  • Artemias 
  • Daphnias 
  • Tubifex 
  • Aquatic insects 
  • Brine shrimp
  • Crickets 
  • Larvae 
  • Romaine lettuce 
  • Zucchini 
  • Boiled peas 
  • Cucumber 

Here’s a link to API’s Tropical Sinking Pellets that I give my bottom feeders. It’s a brand I trust, and my fish seem to perfectly like it. 

And wouldn’t you want to treat your glofish sharks with something nice once in a while?

Here’s a link to Hikari’s Algae Wafer made with pure-cultured spirulina.

It’s got a pretty good concentration of vitamin C that’s known to reduce stress and build immunity against diseases. 

How Often And How Much To Feed Glofish Sharks?

You can give your glofish sharks 1 big meal every day or break it into 2 small meals. 

If you’re giving just 1 meal, give an amount they can finish within 5-6 minutes. And if you’re giving 2 meals, provide an amount they can consume within 2-3 minutes. 

If you find your glofish shark isn’t eating all of the food offered in one go, it’s advised to break them into smaller meals. 

This way, you won’t have to worry much about leftover food polluting your tank. 

And while we’re often preached about being careful not to overfeed, we overlook the fact that we’re sometimes underfeeding our fish. 

This will lead to stunted growth and dull colors. But even worse, it can cut your fish’s life short. 

Recommended Readings!

Glofish Danio Care Guide | Diet, Habitat, Breeding, Accessories

Glofish Tetra Care Guide | Diet, Habitat, Breeding, Accessories

Glofish Betta Care Guide | Diet, Habitat, Breeding, Accessories

Glofish Shark Water Parameters 

  • Temperature: 24-27 degrees F (75-81 degrees C)
  • pH:6-8
  • Hardness:5-11
  • Ammonia:0 PPM
  • Nitrite:0 PPM
  • Nitrate: Below 20 PPM 
  • Water Movement: High
  • Swimming Region: Mainly bottom

The brains behind these fluorescent fish deliberately chose hardy species like rainbow sharks to create glofish. Therefore, they do well in a wide range of environments.

However, adhere to the table listed above to ensure they live the best and longest life possible. 

Rainbow sharks grow 6 inches long. Therefore, they naturally produce a sizable amount of bioload daily. 

Therefore, you need to have a reliable filtration mechanism in place that can get rid of the leftover food and gunk produced every day. 

But it’s unfair and impractical to solely rely on the filter to take care of things. Maintaining the tank’s health is a constant process that requires elbow grease once in a while. 

The tank’s ammonia and nitrite levels must be maintained at 0 PPM, while nitrate levels can go up to 20 PPM as it’s comparatively less harmful. 

If there’s a spike in levels of these harmful compounds, your glofish shark will begin to show signs like reddened gills, panting, darkened colors, red spots, and clamped fins. 

And if you don’t correct the parameters in time, your little sharks will die prematurely. 

We always rely on the API’s Freshwater Master Kit to test the water parameters every week and highly recommend you do so. 

I only recently learned that liquid-based tests are far more accurate than test strips. 

Here’s the link to API’s Master Kit if you are interested:

Glofish sharks aren’t exceptionally difficult to care for as long as their habitat is clean. 

Tanks are closed systems – and irrespective of their size, they all need routine maintenance. Over time, decomposing and organic matter will increase the tank’s nitrate, phosphate, and hardness level. 

You should aim to perform at least 20 to 25% water change every week. But there’s no one hard and fast rule for it. 

Perform water changes based on your tank’s size and stocking number. 

Glofish sharks’ wild cousins, rainbow sharks, live in the high-flow waters of Indochina river basins. 

Thus, to emulate a similar effect in the tank, you might want to add more than just one external filter. Also, adding a horizontal filtration system will help maintain the water flow high. 

Some other methods of increasing the water flow are:

  • Adding air stones 
  • Aquascaping 
  • Adding powerheads and wavemakers 

Now, listen up – here’s an important bit. 

In practically all US states, tap and municipal water contain traces of harmful compounds like lead, mercury, and chlorine to kill harmful microorganisms that plague water supplies. 

However, such chemicals are particularly harmful to our aquarium fish and often prove fatal. 

For instance, when chlorine reacts with ammonia, it produces highly toxic compounds like chloramine that can effectively kill the fish. 

Therefore, it’s super essential to dechlorinate the water first using a reliable water conditioner. 

Here’s a link to API’s Stress Coat Water Conditioner that has over 10 thousand raving reviews on Amazon. I use this one too! 

Before we end this segment, let’s quickly skim through the daily, weekly, and monthly checklist of things you should do to keep the tank clean. 

Daily Checklist 

  • Do a headcount and check your sharks’ behavior 
  • Check the temperature settings 
  • Manually check all the equipment 
  • Remove uneaten food 
  • Top of water level 

Weekly Checklist 

  • Thoroughly wipe down the tank’s outer surfaces 
  • Shake off debris from plants and decors 
  • Scrape the insides of the glass 
  • Siphon the substrate 
  • Carry out water tests 

Monthly Checklist 

  • Trim aquatic plants as needed 
  • Perform all activities mentioned in the weekly checklist 
  • Change the filter media

Glofish Shark Tank Size 

The official site for Glofish states that glofish sharks should be kept in tanks sized 20 gallons or larger. But that’s fake news at its finest. 

Glofish sharks need at least 50 gallons as a bare minimum. Still, the bigger the tank, the better.

And as they are active swimmers, always opt for a horizontal tank over a vertical one. 

As you already know, these fish are highly territorial. 

Keeping them in a small tank directly translates to mass destruction – I am not even kidding. 

Your glofish shark will occupy most of the territory. And the rest of your poor fish will have to cower to one corner of the tank, lead an impoverished life, and wait for their turn to get bullied. 

Besides this obvious drawback, small tanks also come with a host of other disadvantages that directly or indirectly degrade your fish’s quality of life. 

Let me list down the reasons below.

First, small tanks are more prone to get polluted quickly. The buildup of harmful compounds like ammonia and nitrate happens a lot quicker than it’d in a big tank. 

Second, small tanks are way more volatile than their bigger counterparts. Even the slightest fluctuation in one corner – let’s say temperature – can be felt throughout the tank. And no fish likes sudden changes in their environment. It’ll severely stress them out. 

Third, small tanks directly translate to a lack of exercise. And lack of exercise equals stunted growth. So in a small tank, your glofish shark won’t be able to stretch its muscles as much as it’d like to.

Honestly, I can go on and on about how and why small tanks are harmful – especially for fish like glofish sharks. But I think I got my point across here. So, I’ll stop for now! 

Substrate And Decors For Glofish Shark 

Glofish sharks prefer sandy substrate. Their wild cousins are natives to waters lined with sandy bases. 

Dark sand would help bring out their colors the best. 

Also, many hobbyists prefer sand over other options because it’s much easier to clean and rarely collects waste. 

If you prefer gravel over sand, you have to be a bit careful as these fish love to spend a reasonable amount of time at the base. 

Large, sharp chunks of gravel will lead to scratching and eventually infection. 

Also, gravel has a tendency to gather waste. Therefore, cleaning can be quite a hassle. 

Nonetheless, if you choose to use gravel, just make sure it’s on the finer side, and you siphon the substrate regularly. 

As for plants and decors, you must add plenty of them. This will help to manage your glofish shark’s anger management problem. 

They will also serve as a hideout for your subdued fish and lessen the chances of confrontation with the mighty glofish shark.

And even if you keep glofish shark alone in the tank, you will still want to add numerous hiding places made out of caves, rocks, driftwoods, and other decors to make them feel comfortable. 

While adding plants and decor, keep in mind that these fish love to spend a good amount of time at the bottom. So, the tank’s base shouldn’t be very busy. 

As for plant choices, you can add both live and fake plants. If you’re using the latter, make sure they don’t have sharp edges. 

And lastly, don’t forget to add a fitting lid on the tank as these fish make prolific jumpers. 

Recommended Equipment For Glofish Shark 

Glofish sharks may be a hardy species, but raising them does require a tad bit of hefty investment upfront. 

Since they should be housed in huge aquariums, you will need to get your hands on powerful, high-capacity equipment that can handle a big volume of water. 

For the sake of this article, we researched dozens of different products, scoured through hundreds of reviews, and came up with our shortlist for a solid filtration, heating, and aeration system. 

Have a look at them! 

Cascade Canister Filter 1500

What We Love About It:

  • State-of-art flow valves that rotate 360 degrees for easy maneuvering 
  • 5 stackable, large-capacity media baskets for customization 
  • Easy push-button primer for quick and straightforward prime
  • Comes with everything you need to get it started 

Hiccup: 

  • A few complaints about the filter rattling

Hygger Submersible Fish Tank Water Heater 

What We Love About It:

  • Warms within 5 seconds 
  • Intelligent thermostat offers over-temperature protection
  • Anti-dry protection turns off the heater automatically after the water evaporates and the heater is exposed 
  • 3-digit digital display accurate to 0.1 degrees F

Hiccup

  • A few complaints about the thermostat 

Tetra Whisper Air Pump 

What We Love About It:

  • Pumps air down to 8 feet deep 
  • Creates dramatic bubble effect
  • Super quiet operation

  • Hiccup:

Some complaints about loud noise

Glofish Shark Breeding 

I have two pieces of bad news for you. 

First, it’s illegal to ‘intentionally’ breed glofish sharks. 

Second, there have been no documented cases of successful breeding of glofish sharks in the aquarium setting. 

Now, let me explain both points further. 

The official GloFish site reports that you can’t intentionally breed glofish. 

But if you have glofish sharks of both sexes in the tank and they produce little fry, I doubt the company will send you a legal notice. 

Just be sure that you don’t try to sell or barter glofish offspring. 

Next, due to their incredible intolerance for each other, I didn’t find single successful documentation of them having babies even though I scoured the internet for hours. Amazing! 

Apparently, professional breeders often use some sort of hormones or pheromones to encourage them to breed. 

Nonetheless, if you like picking hard battles, you can definitely give it a go. But don’t set your hopes too high. 

Setting Up Glofish Shark Breeding Tank

You will need at least 75 gallons of aquarium space. Once again, if you can go bigger, do it. 

Add liquid de-chlorinator, so it neutralizes any potentially harmful chemicals. 

Add some plants, rocks, and caves that will serve as hideouts for the times your fish feel strained. 

Install an aquarium heater that consistently maintains temperatures between 72-82 degrees F. And add a sponge filter, so it doesn’t suck in your tiny shark fry. 

Next, cycle the tank and try to emulate the same water parameters as the main tank. 

Initiating Glofish Shark Breeding 

Once the tank is fully cycled and prepped, you can add the bonded pair and wait for a week or so to ensure they tolerate each other’s company. 

If they turn on each other, you might want to remove them and experiment with a new pair. 

Feeding protein-rich food like brine shrimp and bloodworms and performing a big water change are also known to encourage breeding.

If you’re lucky, your glofish sharks will soon start exhibiting mating behavior. You can see them circling each other and rubbing against one another. 

The female will lay hundreds of adhesive eggs that will be scattered all over the place. The male will then shortly fertilize the eggs with milt spray. 

Remove the parents as soon as the spawning session is over, so they don’t snack on their younglings. 

Caring For Glofish Shark Fry 

A 75-gallon tank would be too big for little fry. It’ll be super hard for them to find any food in such a big space. 

Therefore, you should transfer the fry to a small tank sized about 10 gallons or so. Move the eggs using a nylon net. 

The eggs will hatch in the next 36-48 hours. The wigglers will then feed on the yolk sac attached to their bodies for much-needed nutrition in the initial days. 

Once the sacs are depleted and are shrunk into their bodies, you will have to fortify their diet with small foods. 

You can give infusoria, baby brine shrimp, egg yolk paste, pulverized flake food, and microworms. 

At this formative stage, fry are very much susceptible to suffer from malnourishment, which can possibly be fatal. 

So, you need to keep a close eye on their feeding behavior. If your fry seem to deter certain kinds of food, you need to immediately switch the food you provide. 

Glofish Shark Diseases 

Glofish sharks, just like their forebears, are exceptionally healthy and hardy fish. Thus, they seldom contract any disease as long as you take care of their diet and environment. 

That being said, we cannot rule out certain ailments that often plague freshwater fish. Some are ich, fluke, bacterial and fungal infections, and swim bladder disease. 

Ich is caused by a parasitic protozoan that’s present in dirty tanks. It manifests as tiny white dots throughout the fish’s body and fins and is super contagious. 

We swear by this Ich-X treatment from Hikari to treat our fish, and it has worked like a charm every time. 

Another common ailment glofish sharks are susceptible to is swim bladder disease. It’s either caused by digestive complications, internal abnormality, or an injury.

The affected fish is forced to swim sideways, upside down, sink to the bottom, or float to the top. 

The treatment for swim bladder disease varies depending on the cause. If it’s due to indigestion/constipation, fasting the fish and feeding fibrous meals can help. 

If an injury or an inborn abnormality are the reasons behind it, you’ll need to seek professional help. 

Most diseases like flukes, parasitic infestations, and bacterial and fungal infections can be kept at bay by maintaining the right water parameters and diet regime. 

Also, remember that any new addition to the tank – be it a new fish, plant, rock, or decor – carry the potential of transmitting unwelcome viruses into the tank. 

Therefore, you should always make a point to thoroughly clean everything before adding them to the tank. 

Although glofish sharks are super resilient to begin with, identifying the signs of illness and treating them early make a big difference. 

This way, the disease outbreak will only be limited to one or a few fish. 

Final Words: Glofish Shark Care Guide 

So, did you find the care guide helpful? We hope you did!

Frankly, glofish sharks aren’t suited for everyone – especially beginners. However, if you have one, it sure is fun to watch their antics. 

Glofish sharks are hardy, just like the original species – rainbow sharks.

 If you get a few things right, they’re not too high-maintenance either. 

Just make sure the fish has PLENTY of space to swim around and claim. And the rest will fall into place!

Recommended Readings!

How Many Glofish In A 30-Gallon Tank? Answers For All 5 Species!

What Do Baby Glofish Look Like? Photos And Videos!

Do Glofish Eat Each Other? Real Answers!

rohit gurung author at urbanfishkeeping

About Rohit Gurung

My never-ending love and fascination with Aquascaping started when I received a red-eared turtle for my 10th birthday.

Apart from researching and writing, I spend hours gazing at my 3 turtles. And yeah, I bask alongside them too.