Rainbow Shark – A Complete Guide (Care, Diet, Facts)

If you are looking for an excellent freshwater fish that will liven up your tank, the rainbow shark could be for you.

The rainbow shark is stunning, yet territorial. So, this fish is going to have a lot of personality, and they are excellent for freshwater tanks if taken care of properly.

If you are interested in learning more about the nature of this fish, keep reading to find our full guide below.


About the Rainbow Shark

The rainbow shark, or epalzeorhynchos frenatum, is a member of the Cyprinidae family. They originate from the waters of Southeast Asia, specifically in Thai rivers. This fish is known as multiple different names including the ruby shark, the red-fin shark, and the rainbow shark minnow.

They are given the common name of the rainbow shark because of the dorsal fin which stands upright giving the appearance of a small shark. These fish usually live to around 5 to 8 years if taken care of properly.

This fish has a dark grey colored body with bright red fins. They are long and slender with a pointed snout. The most prominent fin is their dorsal fin which stands upward giving them a shark-like appearance.

The rainbow shark grows to 6 inches in length. But, like many other species of fish, they are able to grow much longer in the wild when not kept in captivity.

Once fully matured, the female fish will be thicker and the male fish will be thinner. Also, the male fish tend to have brighter coloration and may develop thin black lines of their tail fin.

It is only sometimes possible to decipher which gender the fish is when they are juveniles. Most of the time, in order to be sure, you can only know the gender of the fish when they are fully matured.

A common variation of the rainbow shark is the albino rainbow shark. They are practically the same as the rainbow shark, but their body is white instead of dark grey. They will typically grow to the same size and have all of the same characteristics of the normal rainbow shark.

In terms of behavior, one of the rainbow shark’s trademarks is acting territorial. This can cause negative behaviors in community tanks such as aggressiveness and dominance.

Although these fish like to hide at the bottom of the tank, they are very active swimmers. Therefore, your tank should be on the larger side in order to give them the space they need to swim and be active. Preferably, it should be very long because they love to swim a lot but at the bottom of the tank only. But, you should still provide them with lots of plants and rocks for them to hide and swim through.

Since they are considered bottom dwellers, they will actually eat the algae that lingers at the bottom of the tank.

Like a lot of other active fish, they will try to jump out of the water. So, it is crucial that you make sure your fish tank lid is sturdy and secured properly.

Benefits of the Rainbow Shark

Visually appealing – The vibrant, fiery red coloration on their fins makes an excellent contrast against their black body. Also, it makes a great contrast on other things in your tank such as the blue water and green plants. This coloration is going to make your tank look so much more appealing and beautiful to look at.

They eat algae – Something great about rainbow sharks is that they actually eat the algae at the bottom of your tank. This is very common with bottom-dwellers. This is going to prevent the algae from spreading in your tank which will eventually infect the water and make the environment unhealthy.

Easy dietary needs – The rainbow fish is not picky at all when it comes to food. They are omnivores, so they will eat both meat and plant-based foods. They eat anything you give them such as live food, fresh vegetables, frozen food, pellets, and flakes – just make sure that it will sink to the bottom of the tank. These fish avoid swimming at the top of the tank to get food.

Requirements for the Rainbow Shark

Tank size – The rainbow shark needs a tank at least the size of 50 gallons (preferably larger). Although they are small in size, they need a large space to swim in given their active lifestyle. Also, since they are territorial, they need lots of room so they do not become aggressive. Preferably, the tank should be very long since they prefer to swim at the bottom of the tank only. Another thing to note about the tank is that the lid needs to be sturdy. These fish tend to try to jump out of the water at the top, so keeping your lid secured appropriately is a must for keeping this fish.

Ornaments – The rainbow shark should have lots of plants, aquarium rocks, and driftwood in the tank. Stemming back to their natural environment, they found protection hiding away from everything else. Therefore, they feel most comfortable when they have lots of hiding places. They love things that have holes in them like caves and aquarium rocks with openings. But, it is still very important that you leave an open swimming space in the tank that will help to oxygenate the water in the aquarium. Balance is key here.

Substrate – The best substrate for the rainbow shark is sand. Sand is what is found in Thai rivers which is where they come from. Keeping a natural environment in the tank that is created based on the type of fish you have is going to keep your fish happy, healthy, and stress-free.

Water – Water is one of the most important things in your tank. You have to keep the water at the appropriate levels for your fish to be happy and healthy. For the rainbow shark, the water’s temperature should be between 75 and 81 degrees Fahrenheit. Also, the pH levels should always remain between 6.5 and 7.5 pH, which the hardness of the water should be between 5 and 11 dGH.

Lighting – For the rainbow shark, the lighting should be kept at a medium level. This is going to emulate a natural environment. To further resemble a natural lighting cycle, a light timer is recommended, so you don’t have to remember to turn on and off the light at certain times every day.

Filtration – Filtration is important for every single fish tank, but there are distinctions to filtering a tank with a rainbow shark. It is important that you keep the filter on a medium flow rate. This rate of water movement is going to best resemble a natural environment and help the fish grow and thrive.

Diet for a Rainbow Shark

One of the beneficial things about rainbow sharks is that they are not difficult or picky when it comes to food. They will eat almost anything you give them as long as it sinks to the bottom of the tank. Since they are a bottom-dwelling species, they will not go up to the top of the tank in order to eat. Avoid fish flakes and other free-floating food for this reason.

Rainbow sharks are omnivores, so they eat both meat and plant-based foods. In their natural wild habitat, they usually eat things like plants, algae, insects, and small meat they find in the water such as zooplankton.

You can feed the rainbow shark a variety of different foods such as pellets, frozen food, fresh food, and live food. It is best to vary their diet so they are not always eating the same thing. This will prevent them from having a loss of appetite and not getting all the nutrients they need.

Some foods that fish tank owners often feed rainbow sharks are algae, crustaceans, and zooplankton. These are foods that they would eat in the wild, so they will have no problems eating them.

Also, there are foods you can give them they will enhance the bright red coloration of their fins. These goods include live food, frozen bloodworms, and shrimp.

If you have a juvenile rainbow shark, it is important that you feed them a varied diet. This is going to promote healthy growth and will allow them to thrive as they mature. If you are not feeding juvenile rainbow sharks properly, it can result in stunted growth, faded coloration, and possibly a shorter lifespan.

You should feed rainbow sharks about 2 to 3 times a day, and you should be letting them eat for around 5 minutes each session.

Compatibility & Tank Mates

Finding compatible tank mates for your rainbow shark is not the easiest task. If you are looking for an excellent community fish, the rainbow shark probably isn’t the best fish for you.

However, if kept with certain fish, they can be friendly. It is important that you have a very large tank if blending other species with the rainbow shark, as they can get very territorial. If the fish goes in their territory, the rainbow shark will not hesitate to be aggressive.

Generally speaking, you should choose fish that do not look anything like rainbow sharks. Also, avoid other bottom-dwelling fish since the rainbow shark will probably claim the entire bottom of the tank as its territory.

Pick fish that are able to defend themselves, but make sure they have a calm demeanor. This will make them seem less threatening to the rainbow fish, but if they do happen to be aggressive, the other fish can defend themselves.

Some fish we recommend blending with the rainbow fish are Rainbowfish, Danios, Gouramis, and Barbs. All of these species have solid personalities, but they should not threaten the rainbow shark in any way.

Some fish we do not recommend blending with the rainbow fish are cichlids, catfish, bala sharks, and red tail sharks.

Rainbow sharks should not be kept with other rainbow sharks. Because of their territorial behaviors, they will be very aggressive to their own species. So, just avoid keeping more than one rainbow shark in a tank at a time.

If you decide to blend the rainbow shark which a compatible species, make sure you place the rainbow shark in the tank last. This will help prevent them from immediately claiming their territory since other fish are already in the tank.

However, it is important to remember that you always take a risk with keeping rainbow sharks with any other species, including their own. But, in order to lower the risk of aggression, provide your fish with a large space to swim in due to their territorial nature. This should limit the amount of aggression in the rainbow fish.

Breeding Rainbow Sharks

Unfortunately, rainbow sharks are not easy to breed when kept in captivity. In fact, there are little success stories even out there. This is likely because of their territorial nature making them aggressive and defensive in fish tank settings.

But, in the wild, rainbow sharks breed normally during October/November. This is their breeding season when they reach their full maturity and mate with one another. As a general rule, the rainbow shark is probably not fully sexually mature yet if they are smaller than 4 inches.

Rainbow sharks reproduce when the females lay their eggs and the males fertilize them. When this happens, the eggs will normally hatch within a week.

Final Thoughts

Rainbow sharks are some of the best freshwater fish because of their alluring coloration and active nature. However, they are not great for any community tank because of their territorial nature which makes them get aggressive.

If you are looking to breed this fish or if you are looking for a community fish, this fish probably is not for you.

Giving them an environment that suits their natural habitat is essential for keeping them happy and healthy. If kept properly, the rainbow shark can be a great asset to your freshwater tank.

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