A Beginner’s Guide to Rainbow Shark Care

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Bringing color, attitude, and uniqueness to your aquarium, the rainbow shark fish is a beautiful creature with an eye-catching appearance. 

Looking at one, it can be tempting to buy one for your tank right there and then.

Trust me, I have been there!

However, before you think of bringing a rainbow shark to its new home, there are a few things you should be aware of, such as the fish’s natural habitat, temperament, tank requirements, and much more.

In this beginner’s guide we will go through everything you need to know before and after buying this fish.


Rainbow sharks (Epalzeorhynchos frenatum) are often referred to as red-finned or ruby sharks, thanks to their bright red fins.

The fish originates from Southeast Asia, and is native to tropical freshwater, instead of saltwater.

You will find these fishes usually living in rivers in Thailand, Malaysia and Laos.

Despite what their name suggests, these fish do not actually belong to the shark family.

They are given their name only because their dorsal fins have a shark-like appearance.

They belong to the Cyprinidae family and are classified as Epalzeorhynchos frenatum.


The most prominent feature of a rainbow shark is, of course, its fins. 

Their fins are a rich red color and may even take on an orange hue at times. 

These vibrant fins tend to stand out even more against their dark (grey or black) bodies.

Some of them even have a dark blue body. However, that is not so common.

Rainbow sharks have long and slender bodies.

Their faces are somewhat flat, with a rounded snout in the front.

Their eyes – one on either side of their head – are a bit sunken in.

You may find that their are some color and appearance variations between the male and the female fish.

Male rainbow sharks, for instance, tend to have brighter fins than their female counterparts.

Moreover, male rainbow sharks tend to be slimmer whereas female ones are thicker and have rounder bellies.

These differences in appearances will be apparent to you once the fish mature as their are no noticeable differences in their looks when they are babies.

The Albino Rainbow Shark

Rainbow sharks also has an albino version that has identical red fins as the normal one but has a white or cream body rather than the usual grey or black one.

The body may seem yellow or light pink at times as well.

Coupled with the bright red fins, the light-colored body of this fish makes for an interesting combination due to which the fish is highly sought-after.

Albino Rainbow Shark

Rainbow Shark Size

When rainbow sharks hatch from their eggs, they are not much more than mere specks in size.

From there, the fish grows somewhere between half an inch to an inch in size from two to four weeks.

At its full maturity, their average size is 4-6 inches.

This applies to both males and females.


Rainbow sharks have an average lifespan of about 6 years but they may even live as long as 8 years.

The lifespan of your fish depends largely on your tank conditions.

The better the tank conditions, the more the fish will thrive and consequently, the longer it will live. 

Typical Behavior – Are Rainbow Sharks Aggressive?

Typically, these are territorial fish.

This leads to the fish exhibiting behavioral problems like aggression and dominance, at times.

The aggressiveness generally happens as the fish grows older.

A young rainbow shark is usually very shy and prefers to spend most of its time in hiding.

Moreover, these fish are active swimmers. They swim at the bottom of the aquarium.

For this reason, they are also known as aquarium cleaners as they eat the algae growing at the bottom of the tank. 

Before you bring your new fish home, you should make sure your tank is long and spacious for the fish to swim around in comfortably.

Rainbow sharks swim in higher waters, too.

However, whilst they are peaceful with other fish in higher water, they are generally very aggressive with the fish at the bottom of the tank, including their own kind.

Their aggressive behavior can include anywhere from biting and head butting, to chasing the other fish.

To give them minimal reasons to get aggressive, you should provide a tank with plenty of space and hiding spaces.

One more thing to take into consideration before bringing a rainbow shark home is jumping.

Whilst they do not usually do this, it isn’t unheard of.

To be on the safe side, make sure your lid is well fitted to prevent the fish from jumping out of your aquarium.

Natural Habitat

Rainbow sharks come from the balmy rivers of Indochina having sandy substrates.

They usually swim at the bottom of the surface of the water.

As mentioned above, these fish are fast and active swimmers.

They love to move around a lot in the tank and like their space.

Therefore, getting a tank with a lot of horizontal space is necessary for these fish to thrive.

Typically, adult rainbow sharks should not be kept in tanks smaller than 50 gallons.

If the tank is too small for them, you are going to have a lot of territorial problems to deal with.

Ruby Shark or Rainbow Shark, epalzeorhynchos frenatus

Optimal Tank Requirements

Just like with any other fish, when it comes to caring for a rainbow shark, a few things need to be taken into consideration.

They do not need a lot of special care.

However, I would not suggest beginner aquarists getting this fish.

The fish is more suitable for people who have a few years of experience under their belt.

Tank Size

An average adult rainbow shark needs a minimum tank size of 50 gallons.

This size would obviously increase as the number of rainbow sharks, or other fish, also increase. 

They need space to thrive and live a healthy life.

Therefore, anything smaller than 50 gallons would not be fair to the fish and would affect its health and the health of the other fishes around it.

Moreover, the tank should be at least 4 feet long.

If you plan on keeping multiple rainbow sharks, then it should be no less than 6 feet in length.

Having a good-sized tank will also leave enough space to add rocks, plants, caves, and other substrates like sand, to the tank.

You should also leave a few inches of space on top of the tank to allow for oxygen to reach the rank.

These few inches should be accounted for when looking for the ideal tank for your new fish.

The minimum tank size requirement of 50 gallons increases even more if you want to breed them.

This will provide the mating fish ample space to swim, hide, and enough gravel for the female to deposit eggs.

Water Parameters

If you want your rainbow shark to be safe and healthy, maintaining the right pH levels is vital.

A pH level between 6.5 to 7.5 is ideal for the fish.

Remember to prepare your water and allow it to cycle for a couple of weeks (to stabilize it) before you introduce your rainbow shark into the new environment.

The water temperature should be set between 72- and 79-degrees Fahrenheit.

Tank Mates

As mentioned earlier, rainbow sharks dwell towards the bottom of the rivers they inhabit.

They imitate this behavior in captivity as well.

Which is why you should avoid putting any other fish that tends to dwell at the bottom in the aquarium.

Instead, go for fish that dwell in the middle or upper levels of the tank.

This would avoid any territorial issues and consequently, aggression among the fish.

The following fish could be safely kept along with rainbow sharks:

  • Rasboras
  • Gouramis
  • Rainbowfish
  • Danios

Conversely, these fish types are bad tank mate choices for rainbow sharks:

  • Redtail sharks
  • Catfish
  • Cichlids
  • Bala sharks

As a general rule of thumb, rainbow sharks are not usually aggressive towards other fish that don’t look like themselves.

It is advisable to keep fish that are able to defend themselves from a rainbow shark’s attacks.

You do not want to keep a smaller and weaker fish with these fish.

Compatibility With Other Rainbow Sharks

I would recommend you keep only one rainbow shark per aquarium at any given time.

They do not behave well when they have to live with their own kind and get aggressive as a result.

This is because, in their natural habitat, they lead a solitary life and are not found in groups.

If you keep a larger rainbow shark with a younger/smaller one, they will relentlessly chase after the smaller one until it kills them.

However, if you still wish to keep multiple rainbow sharks, here are a few key points to keep in mind:

  • You should never keep 2 of them. Always keep 5 or more. This way the most dominant among them has multiple fish to chase
Rainbow Sharks breeding

Nutritional and Dietary Requirements

These are omnivorous fish, which means they eat both plants and animals.

Thanks to this attribute, they are not fussy eaters and you won’t have to make a ton of effort to keep up with their dietary needs and choices.

In their natural habitat, they consume all kinds of decaying plants and algae.

They also eat small chunks of meat such as Zooplankton, and insect larvae.

In captivity, they can eat:

  • Flake food
  • Frozen food (frozen bloodworms)
  • Vegetables (lettuce, spinach, zucchini)
  • Plants
  • Live food
  • Brine fish
  • Pellets
  • Tubifex worms
  • Insect larvae
  • Aquatic insects
  • Crustaceans

Given this long list, it would be easy to keep their diet varied.

You should aim to provide them food from all sorts of food sources, similar to what they would eat in their natural habitat.

Providing them with a varied diet is going to ensure that they live a long and healthy life.

Keeping the dietary needs in the forefront of the fish becomes even more important when you are caring for young rainbow sharks.

If you want your juvenile rainbow sharks to grow large with vibrant red/orange colors, give them a diet that is diverse and not restrictive.

As for the frequency, you should feed them 2-3 times per day for about 3 minutes each time.

Rainbow Shark Breeding

They usually mate from October through November in the wild.

However, the exact month for their mating depends more on the length of the day and the temperature conditions.

Reproduction occurs through egg-laying.

Once the eggs have been laid and the male has fertilized them, they will hatch within a week.

Keep in mind that breeding rainbow sharks in captivity is extremely difficult, if not impossible.

The rainbow sharks you find available in shops are bred in commercial farms in Southeast Asia.

Is Your Current Tank Suitable For a Rainbow Shark?

Keeping a rainbow shark in your community fish tank would provide it with a burst of activity like nothing else.

They can get a bit territorial as they mature.

However, that should not stop you from getting a rainbow shark for your tank.

Given the right conditions and dietary requirements, the fish is going to thrive and would likely not cause any problems by getting aggressive.

The best part about keeping these fish is that they are not picky eaters and keeping up with their dietary requirements would be a breeze.

Whilst they are not the highest-maintenance fish out there, they are definitely not suitable for a beginner fish-keeping enthusiast.

You do need to take some extra steps to fully care for rainbow sharks.

However, they make up for that in their beautiful appearance and fun colors.

Photo of author


Irma Bense is the founder of BetterFishkeeping.com. She has over 42 years of experience in keeping fish.She has kept both freshwater and saltwater fish through the years.She has extensive knowledge in breeding numerous species of fish from Show Guppies, Cory Catfish, German Blue Rams to Apistogrammas.You can learn more about Irma on the 'About' page.

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