Rainbow shark: Size, breeding, feeding and tank mates

The rainbow shark (Epalzeorhynchos frenatum) is a freshwater species fish from the Cyprinidae family throughout South East Asia.

This is also known as ruby shark, red-fin shark, red-finned shark, sharkminnow rainbow, labeo green fringelip, whitefin shark, and sharkminnow whitetail.

It is a popular, semi-aggressive fish for the aquarium. Unlike the real sharks belonging to the lineage of Chondrichthyes, the rainbow shark is an actinopterygian.

The Rainbow Shark is a rather difficult to keep tropical freshwater cyprinid. It would be suitable for those fish keepers with a few years of experience looking to expand their aquarium. 

They are known for their territorial character and vibrant bright red fins. 

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Originating from Southeast Asia ‘s warm rivers, they were given Rainbow Shark’s affectionate common name because of their upright dorsal fin, which gives them a shark appearance. 

Rainbow sharks are fish tank-surface and tank-bottom cleaners. Being inhabitants at the bottom and mid-level, they eat leftover fish food, but they also eat the algae growing off surfaces.

They are known to be peaceful in the wild with their own kind, but were known to be aggressive with each other if kept in a tank together.


Here is the scientific classification of Rainbow shark fish

Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Cypriniformes
Family: Cyprinidae
Genus: Epalzeorhynchos
E. frenatum
Binomial name
Epalzeorhynchos frenatum

Distribution and Habitat

Rainbow sharks in Indochina are native to the Mekong, Chao Phraya, Xe Bangfai as well as Maeklong basins.

They live in sandy substrates with water, near the bottom of the river.

This species feeds on algae and plankton and migrates seasonally to flooded areas, then returns to the rivers when the floods are drying up.

Rainbow shark Appearance


Rainbow shark appearance
Image by MerlinSenger at German Wikipedia

The rainbow shark’s body is elongated in black , dark blue, or bright blue. It points to the snout. The abdominal surface is flat.

The fins have a red to orange-red colouring. There is a characteristic brief stripe to the linear area from the gill cover, eye, and mouth.

The Rainbow Shark is a vibrant red / orange fins dark gray fish. 

They have a long, flat stomach with a pointed snout, and a dorsal fin upright. It’s this fin that gives them the look of a shark. 

The Rainbow Shark is a small fish which, when fully matured, you should expect to grow to about 6 inches. 

Their gender is not identifiable while they are juveniles. You have to wait until they reach sexual maturity. 

Once the females are sexually mature, they will have thicker bodies and males develop small black lines on the tail fin. While males will be thinner, they will have brighter colorations in general. 

The Albino Rainbow Shark is a common strain of the Rainbow Shark.


The average lifespan of a rainbow shark fish is 5-8-year of lifespan. However, it is essential to take proper care of your fish will ensure a healthy environment within the aquarium. 

Rainbow shark fish types

The albino red-fin shark or albino rainbow sharkminnow is a variety of white-bodied rainbow shark with red / orange fins.

It closely resembles the temperament and appearance of “normal” rainbow sharks, therefore they share the same common names in the aquarium industry.

These were occasionally referred to as E. Munense, but this is a distinct species that seldom enters the aquarium trade.

The rainbow shark is also one of the varieties of fluorescent, genetically modified fish known as GloFish.

Rainbow shark fish Behavior

The Rainbow Shark is a territorial fish that can cause certain behavioral issues like aggression and dominance. 

This happens usually as they mature. These types of fishes are timid as juveniles and will spend large periods of their time covering. 

They are active swimmers and tend to stay at the bottom of the tank most of their time. They are known as aquarium cleaners because they are bottom-dwellers as they will eat the algae growing on the bottom of the tank. 

You should make sure your aquarium is long and that your Rainbow Shark has plenty of space to swim at the same level.

While they are peaceful with higher-water fish, they are known to fight with bottom dwelling fish including their own. 

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Such behavior may include biting, chasing and butting head-and-tail. 

By ensuring they are placed in a large aquarium, with a low fish to water ratio, you can try to reduce this behavior.

You should also make sure that they have plenty of hiding places like caves, tunnels and other hollow decorations. 

Lastly, although they are not known for jumping, it’s not unheard of. Therefore you should ensure that your lid is well fitted to prevent them from jumping out of your aquarium.

Generally, jumping happens when they’re first placed in the aquarium.

 There are likely to be displays of threat and fighting. This behavior in combat involves butting head-and-tail, and biting too.

A large rainbow shark will chase a smaller one continuously until the smaller one dies, or chase other fish out of its territory, particularly in confined environments such as aquaria.

The risk of the fish hopping out of its tank could also increase. This makes it hard to breed.

This typical behavior is minimized by the provision of hiding places and hollowed decors such as plants or artificial cave-like and tunnel-like aquatic ornaments.

Tank setup

Rainbow Sharks are tropical freshwater fish which originate from Thailand, as mentioned in the overview section. 

They are active swimmers so adults should not be kept smaller than 50 gallons in aquariums. There should be plenty of horizontal space in the aquarium too.

If the aquarium is too small it will encourage them to become much more aggressive and territorial. 

If you’re planning to keep multiple Rainbow Sharks, you should use a tank of at least six feet long, 125 gallons (although we don’t recommend to keep more than one Rainbow Shark per aquarium; more later). 

Because of the territorial nature of the Rainbow Shark, you should make sure your aquarium has plenty of hiding spots for them.

It could be anything like caves, driftwood and rocks treated. 

It also works with dense vegetation and plants. Plants can be used to keep them distracted so conflict can be reduced and algae prevention helps. 

As for the substratum, they are best suited for sand, as this is what is found in their Thai rivers of origin.

Be careful if you intend to use gravel because it can cut the sharp edges. Try to ensure it’s very fine if you decide to use gravel. 

Rainbow shark fish tank size

Finally, ensure your aquarium lid is well fitted, they can try to jump out your fish tank!

Make sure you have quite good amount of tank size and space for your rainbow shark fish on an average an adult rainbow shark thrives in at least 30 gallons of water, with an aquarium length of 48 inches, at a neutral pH range (6.0 to 8.0 pH), with temperatures ranging from 24 to 27 °C (75 to 81 °F), and water hardness maintained at 5 to 11 dH.

They have to have that much space, because they often swim around quickly and terrorize other fish in any tank of this size.

Tank condition

It should be kept in the following parameters: 75 ° F to 81 ° F, 6.5-7.5 pH and 5 to 11 DH water hardness. 

With Rainbow Sharks you must maintain a stable pH level. Sudden changes in pH can result in them becoming more aggressive than usual. 

The lighting should be maintained at medium level, and the movement of the water should be moderate.

Rainbow shark fish tank mates

Believe it or not but, Having a right tank mates  for your rainbow shark fish is very much essential to make sure you are ensuring a healthy environment with the aquarium.

Let me preface this section by stating the Rainbow Shark might not be the fish for you if you’re looking for a calm community fish. 

While they’re going to get along with many other species of freshwater fish, they ‘re very territorial and this can be overwhelming for more shy species like Marbled hatchet fish and Otocinclus catfish. 

They like to take possession of an aquarium area, as mentioned in the aquarium and habitat section above; generally small caves or something which is fancy and has a good space to hide with rocks. 

We sympathize with any fish stumbling upon the territory of a Rainbow Shark! They are going to be extremely aggressive and chase away the intruders.

Rainbow shark fishes are compatible with upper- and middle-tank dwellers Barbs and Rainbowfish. They may live with danios, loaches, plecos, rasboras, and gouramis as well.

They are not compatible with smaller, more timid fish in the tank, as they may be terrorized by the sharks chasing them out of their territories.

Rainbow shark feeding

Rainbow Sharks are Omnivores as mentioned in the overview, meaning they eat both plants and meat. 

They generally consume decaying plants, algae, insect larvae and small chunks of meat in the wild such as zooplankton that they find in the river. 

They ‘re not fussy eaters, and they’re going to consume most of the stuff; providing it sinks to the tank bottom! 

If you plan to keep Rainbow Sharks in aquariums this is good news. They’ll have no complaints eating flake food, frozen food, pellets, vegetables and live food. 

You should aim at keeping your diet varied and feeding them a variety of sources of food, similar to what they would eat in the wild.

For example: algae (tables or wafers), larvae of insects, crustaceans (frozen or live), and zooplankton.

You can also offer them plenty of vegetables like spinach, lettuce, zucchini and peas to keep their diets varied; this will keep their immune system strong. 

You may want to check out this article on oscar fish

If you want to make sure that their red / orange color is a vibrant shade, you should give them regular meals of live and frozen meat; frozen bloodworms and brine shrimp are going to be fine. 

For juvenile Rainbow Sharks this is even more essential. If you want your juveniles to grow big with vibrant colors, make sure they have a varied and never too restricted diet.

Rainbow shark fishes are not picky herbivorous and omnivorous eaters, but in the form of tablets, wafers and flakes they are primarily consumers of algae.

They also eat foods that are alive, such as insect larvae, tubifex worms, periphyton, crustaceans, phytoplankton, zooplankton, and water insects.

Diet includes spinach and lettuce too. Also, they’ll eat frozen bloodworms and shrimp brine.

Rainbow shark fish Breeding

It is necessary for an Aquarist to make sure they are aware of the breeding process with their rainbow shark fish. Reproduction is a normal process with living organisms. In this section we will talk about the breeding process of rainbow shark fish breeding.

Rainbow Shark’s in the wild tend to match during October to November, which is when they reach their sexual maturity too.

However, by changing seasons, the exact month can be affected and depends on the length of the day and temperature. 

Rainbow Sharks reproduce by laying eggs. The female lays eggs and then the male fertilizes them by sprinkling the eggs with its milt. The eggs will hatch from here within a week. 

Unfortunately, however, it is extremely challenging to breed Rainbow Sharks in an aquarium and we are yet to hear of any success stories.

Again, this is more than probable in confined settings because of their aggressive and territorial nature. 

Most of the Rainbow Sharks that you find available for purchase will be bred in Southeast Asia based commercial farms.

No actual sequence of breeds was documented in an aquarium setting. Although known to be egg-layers, in an aquarium setting it is difficult to reproduce the rainbow sharks.

Large numbers are being bred in commercial farms in south-east Asia.

Note: If the fish is much less than 4 inches in length, you can assume they are not yet sexually mature. 

Full grown size of rainbow shark fish

Male rainbow sharks have thinner bodies along its tailfins, with black lines, compared to the females. Males also get brighter colouring. They may grow to about 6 in (15 cm) in length.

Rainbow shark fish price

usually, As for the cost you should seek to spend no more than $3 per fish and they are readily available throughout the year. However, The price may vary on availability due to seasonal changes.

Concluding Thoughts

Rainbow sharks are not recommended to the new aquarist because of this behavioral characteristic among their own kind.

It should be avoided to keep them with relatives, such as red-tailed sharks, bala sharks and black sharks, as they will also chase and attack them.

Is the Shark Rainbow Right To Your Aquarium?

The Rainbow Shark would make a great addition to your community, as long as they don’t have the same or similar looks of fish. 

While they are known to be territorial, as long as you provide them with an appropriate aquarium environment and match them with the appropriate tank mate(s), you should not have too many problems with them. 

They are a beautiful fish and an active swimmer, so enjoy watching them in an aquarium will give you pleasure. 

They are good eaters and will eat various forms of food including pellets, flakes and frozen meat.


Hey, I am Praful Kharade, a Blogger, a Data scientist, and the Founder of Planet Fish. This is one of my Hobby Blogs that focuses on Aquatic animals, Reptiles, and Fish Keeping.

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