Rainbow sharks are a fun and unique fish that can be very rewarding to keep.

However, there are some things you need to know before you think about getting one for your tank.

In fact, the rainbow shark might be one of the most misunderstood fish in the aquarium world (especially by beginners). 

In this guide we go over their origin, behavior, appearance, and how to care for them.

What Are Rainbow Sharks?

Sometimes referred to as a red-finned or ruby shark, the rainbow shark is native to Southeast Asia. They are not a saltwater fish but instead, thrive in freshwater. In particular, they live in the rivers of Myanmar, Thailand, Laos, and Malaysia.

They prefer rivers with sandy bottoms and plenty of plankton. However, they are also known to migrate into floodplains during periods of heavy rain or flooding.

Rainbow sharks are not true sharks. Instead, they are given their name because they have a shark-like appearance due to their dorsal fin on top.

True sharks also belong to the Chondrichtheyes family, but rainbow sharks are part of the Cyprinidae family, which is the same family as minnows. They belong to the cypriniformes order and are classified as Epalzeorhynchos frenatum.

This species was once abundant in the waters of Southeast Asia, but have dwindled in numbers in recent years. Scientists believe that the damming of certain rivers such as the lower Xe Bangfai has led to fewer rainbow sharks in recent years.

River dams may decrease floodplains and may therefore interfere with the ruby shark’s breeding patterns. The aquatic trade has little effect on their numbers in the wild as just about all commercially-available rainbow sharks originate from farms in Thailand.

Appearance

Of course, rainbow sharks are well known for their red fins, which is primarily what gives them their name. Aside from being red, their fins may sometimes take on an orange hue as well. 

Their colourful fins stand out even more against their gray or black bodies, which tend to be very long and slender. Some rainbow sharks will also have a dark blue body, although this is somewhat less common.

These fish have dorsal fins that may consist of up to 11 branched rays, along with a forked tail fin.

The rainbow shark’s face is rather flat, with a somewhat rounded snout in front. There are two eyes, one on either side of the head that often appear to be sunken. The rest of the rainbow shark’s body is rounded near the head and back and then tapers off as it nears the tail.

There is some colour variations between males and females. For example, males tend to have brighter red or orange fins than females do.

Males will also have thin gray lines on their tail fins, while females will not have any lines. 

Female rainbow sharks also tend to be thicker and have more rounded bellies. These become apparent as the fish mature as there is basically no difference between juvenile male and female rainbow sharks.

You’ll have to wait until the fish are sexually mature to distinguish males from females.

The Albino Rainbow Shark

There is an albino version of the rainbow shark. This fish has the same red fins as the rainbow shark but has a white body rather than blue or black markings.

Sometimes, the body of an albino rainbow shark will take on a light pink or yellow hue as well. The light-coloured body contrasted with its brilliant fins gives the albino rainbow shark a unique, yet highly sought after appearance.

General Behavior and Temperament

In their natural habitat, rainbow sharks are rather passive and do not really prey on other fish or aquatic animals.

That doesn’t hold true in captivity however. 

When given the right amount of space, rainbow sharks will typically get along well with other freshwater fish. With that being said, there are certain fish that should not be placed in a tank along with rainbow fish.

Some rainbow sharks are also naturally more aggressive than others and may become more territorial with age. As such, you should always use caution when introducing your rainbow shark to other fish.

Due to their territorial nature, these fish are not recommended for beginners.

Average Rainbow Shark Size

The size of a rainbow shark at full maturity is typically no longer than 15cm long. There are some that have grown to be as long as 20cm in length, but those are an exception.

This size holds true for normal rainbow sharks as well as the albino varieties. Both males and females tend to be about the same size in length.

The main difference between males and females when it comes to their shape and size is that males are a little more slender.

When rainbow sharks hatch from eggs, they are not much more than mere specks. From there, they grow rather rapidly.

Between two and four weeks of age, the fish will have grown to somewhere in the1-2.5cm range. It can take several weeks or even months for them to reach their full size.

A red-finned shark is considered sexually mature when it is at least 10cm long, but may nonetheless continue to grow after that.

Lifespan

The average lifespan of a rainbow shark is between four and six years long, although some have been known to live for as long as eight years.

That’s much longer than other aquarium fish such as bettas, which may only live for about two years. However, it is much less than goldfish, which can have a lifespan of up to twenty years.

The quality of water in your tank is a key factor in how long your rainbow shark will live. If your water supply has high levels of chlorine or chloramine, you may need to treat it.

Rainbow Shark Care

There are a few things you need to consider when it comes to caring for rainbow sharks. Overall they are tough little guys and don’t need to be babied, but that’s assuming you take care of their essential needs.

Below we highlight the main areas that you need to focus on when it comes to rainbow shark care.

If you stick to these guidelines you’ll be well on your way to ensuring that your rainbow shark lives a happy and healthy life.

Tank Size

The ideal rainbow shark tank size is 189L (at minimum). This will obviously increase depending on the number of other fish you keep in your tank, but in our opinion, you shouldn’t consider anything smaller.

To go smaller is not fair to them or any other fish you plan on keeping in the same tank. Rainbow sharks need space to thrive and feel like they’re in control of their territory/area of the tank.

The tank itself should be at least 1.2m long and 45cm wide if you are only keeping one fish. 

This will give your rainbow shark plenty of room to swim around in. If they don’t have enough horizontal space they’re more likely to become aggressive and feel cramped.

When in doubt, always switch to a bigger tank. Although a 189L tank is recommended, you’ll have even better luck if you go with a 208L or larger.

Ideal Tank Mates For Rainbow Sharks

In their natural habitat, rainbow shark dwell near the bottom of rivers.

This means they also tend to dwell near the bottom of their tanks, and may also stake claim on caves, tunnels, or any hiding area down there.

Accordingly, you should avoid placing rainbow sharks with tank mates that tend to dwell on the bottom as well.

A shortlist of fish that make terrible rainbow shark tank mates are:

• Bala sharks
• Red tail sharks
• Cichlids
• Catfish

• Rasboras
• Danios
• Gouramis
• Loaches (this can be dicey if you have a particularly aggressive rainbow shark but it’s usually fine)
• Rainbowfish

What Do Rainbow Sharks Eat?

In their natural environment, rainbow sharks are mostly omnivores that eat a lot of algae, larvae, and bits of meat.

In an aquarium, they will also eat any algae that naturally forms at the bottom of your tank. You can also give them algae in tablet, flake, or wafer form if there isn’t enough inside your tank for them to dine on.

While algae is a common part of the rainbow shark’s diet, they require a balanced diet.

Some great food choices that they’ll enjoy and help them stay healthy are:

• Frozen bloodworms
• Fish granules
• Brinefish
• Insect larvae
• Tubifex worms
• Crustaceans
• Aquatic insects

Ideally, you should feed your fish a variety of plant and animal material. Perform feedings at regular intervals approximately two or three times each day.

Water Details

Maintaining the right pH levels is very important if you want the best for your fish. Rainbow sharks do best in water that is between 6.5 and 7.5 pH.

Before introducing them to a new tank environment, prepare your water and allow it to cycle for at least two weeks so that it has time to stabilize. Use a heater to bring your water temperature to between 22 and 26 degrees Celsius.

Upon bringing your rainbow shark home, place it immediately into your tank using a net. You don’t want it to spend more inside its transport bag than it has to.

Doing this will prevent shock and provide your rainbow shark with the best possible environment in which it can thrive.