The Ultimate Rainbow Shark Guide: Size, Diet and More…

The Rainbow Shark is an incredibly beautiful, agile, and active species.

Unfortunately they do not possess all colors of the rainbow, however, you won’t be disappointed by their striking appearance.

Are you looking for a more challenging species to care for next?

Keep reading to learn everything you need to know about this fish including tank mates, diet, lifespan and much more…

Rainbow Shark

Key Facts
Common Names: Red fin sharks, Ruby sharks, Rainbow sharkminnow
Color Forms: Black or dark grey bodies with bright red or orange fins – also albino varieties.
Size: 6 inches
Lifespan: 5-8 years
Minimum Tank Size: 50 Gallons
Tank Mates: Not Compatible
Distribution: Southeast Asia

What is a Rainbow Shark?

Albino Rainbow Shark

The Rainbow Shark (Epalzeorhynchos frenatum) belongs to the family Cyprinidae, and is a fun but aggressive tropical fish.

Although they come from a line of aggressive and territorial cousins, they are one of the least hostile freshwater minnows. Despite their semi-aggressive behavior they have gained popularity because of their stunning appearance and the fact that they are not too difficult to care for. They even made our list 25 most popular freshwater fish.

While they are called sharks, they do not belong to the same family. They get their name from the shape of their dorsal fin.

They have a dark black slim body with bright orange fins and a pointed snout.

In an aquarium you can expect their lifespan to be 5-8 years.

They will grow to around 6 inches and can be purchased for anywhere between $4-$7.

Pros

  • They are extremely active which makes them fun to watch.
  • This fish is not a fussy eater and will eat a variety of food.
  • Their contrasting colors give them an exciting appearance.
  • As bottom-dwellers and help to keep the tank clean.
Cons

  • Unfortunately they can be territorial and aggressive.
  • Very limited choice of tank mates.
  • They need a large tank with lots of horizontal space.
  • Not suited for first time keepers.

Rainbow Shark Appearance

Rainbow Sharks are slim bodied fish.

They are well known for their large raised dorsal fin.

In addition to their dorsal fin they have a forked caudal fin, one pair of pectoral fins, one pair of ventral/pelvic fins and one anal fin. If you look at the base of their caudal fin you will notice they have a large black blotch.

Their body is a dark black or gray and their fins are bright red or orange. Interestingly though unlike other fish they have skin, not scales.

Once fully grown they will typically reach around 6 inches, however some specimens have reached 8 inches.

It is almost impossible to tell the difference between males and females until the juveniles become sexually mature. Once sexually matured the females will have thicker bodies. Also the males tend to be brighter than the females and will develop dark lines on their tail fins.

Albino Rainbow Shark

One of the most common color varieties of this fish is the Albino Rainbow Shark.

The Albino is very rare but is starting to gain popularity among hobbyists. Their bodies are pale white and they have bright orange fins. This unique coloring makes this variety very desirable.

Similar Species

There are two species that have a similar appearance:

  • Black Sharkminnow (Labeo chrysophekadion): This species has a similar shape, but the most obvious difference is the absence of bright orange fins. The Black Sharkminnow is a solid dark black or blue color.
  • Red Tail Shark (Epalzeorhynchos bicolor): This critically endangered species has similar colors. However, they only have a brightly colored tail. Their body is a solid black color, along with their caudal, pectoral, anal and pelvic fins.

What Do Rainbow Shark Eat?

Similar to other bottom dwellers, Rainbow Sharks are omnivores.

This means they will eat both plants and prey.

In the wild they scavenge for food and primarily eat decaying plants and algae. When available they also eat insect larvae and zooplankton. In captivity they are not fussy eaters but require a variety of food for a balanced diet and to remain healthy.

If your Rainbow Shark has companions then make sure you buy sinking pellets and flakes so that they have the chance to feed after the top dwellers of the tank.

This species will eat any growing algae in the tank but you should still include algae wafers for their diet as this is what most of their diet consists of in the wild. You can even add peas, lettuce, spinach and zucchini to their diet to improve their ability to combat diseases.

For juveniles it is even more important to ensure their diet is balanced and has a lot of protein. The meaty food in their diet makes their colors develop and become brighter as they mature.

As bottom-dwellers, they will eat anything and everything that is available to them. This makes them an easy species to overfeed which can lead to some of the illnesses described earlier. To avoid this, start by feeding them once a day for a few days to understand what food portions would be best. If food is left over then continue to feed them half the portion, twice daily.

Normally 3 feeding sessions a day consisting of 5 minutes of feeding works best.

What Food Can They Eat?
They are not picky eaters but will need a diet full of different varieties of food sources to keep healthy.

Rainbow Shark Eating

Here is a list of foods that you can incorporate to their diet:

  • Insect larvae
  • Algae (tablets/wafers)
  • Bloodworms
  • Tubifex worms
  • Brine Shrimp
  • Daphnia
  • Artemia
  • Pellets
  • Flakes
  • Vegetables (peas, zucchini, lettuce and spinach)

Always remember to clean and remove uneaten food from the tank to prevent any rot and change to nitrate levels.

Natural Habitat and Tank Conditions

Rainbow Sharks are native to Southeast Asia (Myanmar, Thailand, Laos and Malaysia).

They inhabit the tropical freshwater river basins in the Indochina region including Mekong, Chao Phraya, Xe Bangai and Maeklong.

These soft water rivers have a sandy substrate and Rainbow Sharks will spend the majority of their time dwelling in midwater and bottom depths.

Because they are omnivores, in the wild they make the perfect scavengers. They will feast on algae and plant matter as well as animal remains and small invertebrates.

The sandy bottoms of the rivers make the perfect spots for grazing for food.

If you want to keep them healthy, you will need to closely mimic this habitat.

Aquarium Set Up

Tank Parameter Requirement
Minimum Tank Size 50 Gallons
Tank Type Freshwater
Temperature 75-81°F
pH 6.5-7.5
Hardness 5 to 11 dGH
Flow Medium
Substrate Sand with fine gravel

To get started creating the perfect tank conditions it is important to note the ideal water parameters (above) and equipment.

You should keep the water between 75-81°F, with pH levels between 6-8 and water hardness maintained at 5-11 dGH.

It is best to stick to a fixed temperature, pH and water hardness level within the given ranges because any changes in these conditions can cause unwanted stress and aggressiveness.

You will also need to keep the water flow moderately fast. In long aquariums this can be difficult to maintain so you will need an internal and external filter. You can also use air and water pumps. As for lighting, they have no specific requirements. Medium LED lights will be a great fit (especially if you are going to keep live plants too).

The best substrate for Rainbow Sharks is a fine substrate, such as sand and very fine gravel.

For decoration you can use live plants, treated driftwood and stones to create hiding spaces – this will keep them comfortable and help prevent aggression towards other tank mates.

Live plants are the best option for this species and always look the best. Here are a few plants that would be a great fit:

  • Java Fern
  • Vallisneria
  • Java moss
  • Hornwort
  • Lemon Bacopa
  • Broad Leaf Amazon Sword

Just make sure you do not overcrowd your tank because this can affect the speed of water flow.

What Size Aquarium Do They Need?

Although this species is small they can be highly aggressive and territorial.

Because of this they each need a large amount of space.

For a single Rainbow Shark the minimum tank size required is 50 gallons. They are very active swimmers so it is also important to make sure they have enough horizontal space (at least 48 inches).

If you decide to keep more than one Rainbow Shark then you should use at least a 125 gallon tank.

Best Tank Mates For Rainbow Sharks

In the wild they are commonly found with loaches and plecos. However when you keep one in an aquarium their temperament changes making them very territorial which can cause aggression.

Because of this it is generally recommended that tank mates should be avoided.

However if you really want to keep tank mates then there are a few rules to follow.

It is best to introduce a Rainbow Shark to a freshwater tank that is already occupied. This helps lower the likeliness of aggression.

The most compatible species are middle and top occupying species such as:

  • Danios
  • Rasboras
  • Gouramis
  • Barbs
  • Rainbowfish
  • Clown Loach
  • Indian Loach
  • Snails

Any other species you introduce into the tank should have a strong personality.

Shy species are easily overwhelmed and stressed by aggression, so it is best to avoid these.

It is also important to avoid any other bottom dwelling species such as: Red Tail Sharks, Bala Sharks, Cichlids, bottom-dwelling loaches, and bottom-dwelling catfish. So that means no mixing them with Convict Cichlids.

Because Red Tail Sharks and Bala Sharks look similar to them, Rainbow Sharks will try to assert dominance in the tank.

Overall you should keep them alone unless you have a particularly large tank (125+ gallons).

Keeping Rainbow Sharks Together

As previously mentioned, they are extremely territorial.

Once they have established their territory they will defend it rather aggressively (especially against others in the same species).

If you do want to keep Rainbow Sharks in the same aquarium you will need a large tank (125+ gallons). Even then it is probably for the best to keep them without other Rainbow Sharks.

Rainbow Shark Care

Rainbow Shark In Tank

If you keep these water parameters stable then they are a fairly hardy fish.

However, this does not mean they are immune to disease. Like other freshwater species they can be susceptible to common diseases such as White Spot Disease (popularly referred to as the Ich). This disease is caused by a parasite that makes white spots appear on the mouth, gills and fins.

You will also notice them itching against objects in the tank before these spots appear.

They can also be prone to swim bladder disease which is caused by many different things like parasites, diet and cysts. The symptoms include changes in their swimming behavior and them being unable to keep upright and swimming upside down.

Other illnesses are bloat and constipation which can be caused by diet.

Make sure to perform regular water changes each week and pay attention to any changes in the water quality.

Preventing illness and disease through cleanliness and water changes is much easier than trying to cure illness and disease.

Behavior

Rainbow Sharks are active and agile bottom dwellers.

In the wild they tend to be more relaxed because they have lots of water to swim in, however in the aquarium it can be stressful for them and bring out their aggressive side.

It is very important to keep an individual of this species in a tank that is suitable. This allows them to feel free and not threatened.

Once fully mature they are triggered to assert dominance in the presence of other fish.

It is common for them to attack other fishes that enter their territory.

To prevent this, you can make tunnels, caves and crevices for hiding spaces.

You can also make use of dense vegetation for the safety of the other fishes and for their wellbeing. This will allow a stable community to thrive with less chance of fishes interacting with the Rainbow Shark.

Although they are bottom dwellers they will occasionally wander to the middle or top of the tank. They have even been caught trying to leap out of the tank at times!

Breeding Rainbow Shark

Unfortunately there are almost no recorded cases of successfully breeding a Rainbow Sharks in a home aquarium.

Due to their aggressive behavior and incompatibility of living peacefully together in a school, there are no set guidelines for captive breeding.

There are problems with pairings and hormone production in home environments. The ornamental trade of Rainbow Sharks depends on the import of fry from Southeast Asian commercial fish farms. To try and replicate these commercial farms and hormone injections in home aquariums is very difficult and expensive.

What we do know about wild breeding is that Rainbow Sharks are egg laying.

If the female is accepted by the male then they will start mating behavior such as rubbing against each other.

The female will then lay her eggs and leave, while the male stays to fertilize them. The eggs will have to be placed into a separate tank and the fry will emerge after one week. While the fry grows they must be fed a variety of food including high quality protein to make sure they grow to develop bright and bold colors.

Species History

Not much is known about the history of Rainbow Sharks.

What we do know is they originated in Southeast Asia and were first documented by Henry Fowler in 1934.

They were recorded to be widespread over Thailand, Laos and Cambodia. However, at present time, little is known in the extent of distribution in Southeast Asia. This is arguably due to the aquarium trade and overfishing for exportation but no evidence has been found to support this.

Back when they were first discovered they were known as Labeo frenatus.

However over time due to changes within Genus (based on morphology and other characteristics) their name was changed and they are now referred to as Epalzeorhynchos frenatum.

They were first introduced into the aquarium trade in the early 1990s and were considered to be saved from extinction by commercial breeders. Interestingly the initial appeal of this fish was that it was sold as an alga eater.

Should You Keep Rainbow Sharks? (Summary)

The Rainbow Shark is a stunning and captivating species for any large and unoccupied tropical freshwater tank.

Although they are not the most aggressive fish species out there, this species certainly does have a temper. Because of this they are not the most social of fish but are known to be compatible with middle and top-level dwellers that also have a bit of an attitude.

Diet and water quality changes are often the culprit for any illness or disease in this species so regular partial water changes and water testing is needed to keep this under control.

Once their requirements are met and their lonesome nature is understood, they can be one of the most hypnotizing species to watch.

Do you have the space, time and attention to care for a Rainbow Shark? Let us know below…

About David Thomas

David Thomas David has been keeping fish since he was a child. In his first tank he kept goldfish and since then he has kept over 30 different species. Now he has 4 separate tanks and his favorite is a 100 gallon freshwater tank with a school of Rasboras, Tetras and Loaches.

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