April 19

Rainbow Shark: Habitat, Behaviour and Feeding and Breeding


Rainbow Shark

Rainbow sharks stand out among other cyprinids for their dark grey elongated body, red fins as well as the raised dorsal fin. They are native to Southeast Asia where they dwell in warm rivers.

The minimum tank size for housing them is about 190 litres as they are active swimmers. Items such as caves, plants and driftwood should not be left out of their tank. They are a good choice of fish for aquarists looking to take their aquarium hobby up a notch.

Rainbow may be cool at all times, but these fish are not always so; they exhibit some degree of territoriality and aggression. Their bottom-dwelling nature makes them good tank cleaners as they rid the aquarium of algae.

This article covers facts about the lifestyle, feeding habit, features and compatibility of the rainbow shark. Plus, you will also be acquainted with the breeding pattern and care guide of the fish as you read on.


The Rainbow Shark popularly referred to as the Red-Finned Shark or Ruby Start is a stunningly beautiful fish with fins that are in dark grey to black with reddish colour tones. Scientifically known as Epalzeorhynchos Frenatus, these fishes are semi-aggressive and territorial in nature. Rainbow Shark will be a good choice for an aquarium if you do not introduce any other sharks in the tank. Sometimes they become contentious towards their own species, so it would be better to have only one fish of this breed in a tank. Also, as Rainbow Shark is dominant in nature, it will be better to have other species of fishes that are similar in size.

They are tropical freshwater fishes that are native to Thailand. For beginners, this fish breed is a little difficult to maintain, so it would be better if you have first got some experience in fish keeping and then introduce Rainbow Shark in your aquarium.

If you have decided to add Rainbow Shark to your aquarium then you will need a large tank as this breed likes to set up territories around in the tank.

The Rainbow Shark has a lifespan of 5-8 years and they can grow to a maximum length of 6 inches or 15 cm. In order to keep this breed happy and active, add a lot of rocks, vegetation and driftwood in your aquarium which will help them mark specific territories and avoid fights with other fishes.

Physical features

If you have seen ocean sharks, then you will find the Rainbow Shark strikingly similar in appearance to them. This breed of fish is small in size with an elongated back, flat stomach and upright dorsal fin. The snout in the Rainbow Stark is pointed and the fins are in red or orange colour. The fish has two huge eyes on a small head and the mouth has two pairs of barbells and ceratoid.

You have to wait until the fishes grow completely to identify their gender. The males have brighter coloured and thinner bodies with black lines along with their tailfins. Female fishes have a thick body with a fat pronounced abdomen and faded colouration.

Another commonly found varieties of this breed are the Albinotic type of fishes with red eyes and fins. The Albino Rainbow Shark for particular has a whiter body and orange or red finds. This fish type is almost similar to Rainbow Shark.


These natural habitats for these fishes are the balmy Rivers of Indochina with sandy substrates, where they float in the bottom surface of the water mostly. The water where they are found has a pH of 6-8 and hardness up to 12 degrees.

These fishes are fast swimmers and like to move a lot in the tank, so make sure to have a bigger tank with a lot of horizontal space so that they do not get territorial.


This fish breed is slightly aggressive and shows dominance which happens when they get fully matured. They are rarely peaceful with their own kind and with other species, they get combative. They try to bite other fishes which can cause fin rot. That is why it is extremely important to give them good space in the aquarium to swim freely. Also, give these fishes a lot of hiding space by providing dense vegetation, artificial caves and tunnels in the tank.

The Rainbow Sharks in their natural habitat have the tendency to roam around at the bottom. Similarly, in tanks as wells, they swim at the bottom and feed on the algae which makes them ideal tank surface cleaners. However, with this habit, they also tend to get in fights with other fish species which dwell in the bottom of the aquarium. A large rainbow Shark will chase the smaller fishes out of its territory until the other fishes die. To get rid of this issue, you can introduce other fishes that have the habit of dwelling in the upper side of the tank; maintaining a good fish to water ratio will also ensure good health for all the fishes.

Another important fact about these fishes is that they have the practice to jump which normally happens when they are placed in the aquarium in the beginning. So, to avoid them jumping out of the tank, make sure that the lid is properly placed.


    If you are looking for an alluring and exquisite breed of fish to add life to your tank, then this breed of fish will be a perfect choice, however, for inexperienced aquarists who are just beginning to have fishes, the Rainbow Shark isn’t the ideal breed because this fish likes to dominate and gets aggressive in the presence of other breeds.

    These fishes are very particular about their space and protect their territory from all the fishes in the tank. For Rainbow Shark lovers, it is advised not to populate the tank with too many fishes; otherwise, the smaller ones will definitely suffer.

    Also, avoid fishes that dwell in the bottom of the tank. They are compatible with Raspboras, Danio, Clown Loach and Plecos which are mostly upper and middle tank dwellers. While choosing the tank mates, make sure to have such fishes which are big enough to defend themselves.

    You should also avoid any similar looking fishes as Rainbow Shark doesn’t like living with its own kind and will try to chase away the smaller fish.

    Even if you prefer keeping only Rainbow Sharks in your tank, then provide them with a lot of space so that they have different territories. Because of their hostile behaviour, it gets a little difficult to choose tank mates for them with whom these fishes can be somewhat compatible.


    When it comes to food, Rainbow Sharks are not very finicky; in their wild habitat, they tend to eat a lot of decaying plants and algae. These fishes also eat insect larvae, phytoplankton, tubifex worms and crustaceans. Primarily, these fishes are omnivores, so it is easy to feed them both plants and live food.

    However, for good colouration and a longer lifespan, you should feed plants to your fishes mostly. You should make sure that the food reaches the surface of the aquarium as these fishes are bottom-dwellers. To maintaining the vibrant red or orange colour in your fishes, give them live food more frequently starting from when the fishes are juveniles.

    This breed needs a diverse range of foods to remain healthy. You can feed your fishes vegetables like spinach, peas and lettuce; flake food, pellets, brine shrimp, blood worms and live food. Just make sure to give them a variety of food options instead of sticking to just one thing because lack of food variation can cause retarded growth in the fishes.

    Do not overfeed your fishes; you can feed the fishes twice a day for a duration of 5 minutes. Also, don’t forget to keep an eye on the tank so that you can remove the organic waste from time to time.


    Unfortunately, the Rainbow Sharks haven’t been bred in the tank conditions successfully until now. In their natural habitat, females lay eggs and to fertilise those eggs, the male fishes spray on them. Post spraying it takes 5-7 days for the eggs to hatch and almost 2-3 weeks for the Frey to mature.

    As we discussed in this post, the Rainbow Shark can hardly tolerate its own kind in an aquarium that is why keeping another fish for breeding gets difficult. Additionally, even if you have a huge tank to accommodate a couple of fish, then for successful spawning, the fish will need stimulation with gonadotropic hormones. Even though these fishes are egg layers but because of their extreme territorial nature, they do not allow any other fishes in their area.

    Also, this breed is a river fish and it is not possible to create such conditions in an aquarium. Given the complicated requirements, breeding them at home is highly unrealistic. Most of the fishes are bred in fish farms or by gonadotropic injections.

    Tank requirements

    If you have decided to get a Rainbow Stark for your aquarium, then there are a number of specific needs that you have to take into consideration.

    • The most basic requirement is to have clean water in the tank, therefore clean the water weakly and make sure to get rid of leftover food waste.
    • In the wild, the Rainbow Sharks have sandy substrates in the rivers where they are found, so it would be great to mimic such an environment in the tank by providing them with sand and fine gravel.
    • The water pH should be neutral between 6-8, any sudden increase in pH can make them more aggressive
    • A water temperature of around 25 degree C is perfect for this breed. It is important that the temperature of your tank remains fixed most of the times as constantly changing temperature can cause stress to your fish.
    • The hardness of the water should be maintained at 5-11 dH.
    • As these fishes are very active, you need a tank with a minimum length of 50 inches and 40 gallons of water.
    • Include a lot of plants, driftwood, caves, tunnels, flower pots, ceramic tubes and snags in the tank as Rainbow Stark likes to dwell in the bottom only. You can use fake plants too with softer edges. This will also make the fish comfortable and keep them distracted which will lead to lesser fights with other species.
    • In the rivers, these fishes are used to water that flows at high speed. You can keep the water movement in the tank between moderate to fast.
    • You can use LED aquarium lights at a medium level which will be good for the live plants too.

    Even though for a new aquarist, this fish breed sounds like a lot of work, but with little experience, Rainbow Shark can be a great addition to any tank. These fishes have temperament issues which make them non-ideal for small tanks. However, if you are ready to provide them with a bigger tank and lots of space, then the fishes will be quite happy and active.


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