Rainbow Shark Stats InfographicThe Rainbow Shark also known as Red Fin Shark is one of the true tiny terrors of the freshwater aquarium. Highly territorial and aggressive against its own species, the Rainbow Shark poses a fun challenge to any fishkeeper with a few years of experience. In this article, you’ll learn all about the Rainbow Shark and what it needs to thrive in your aquarium.

Stats and Facts

Here’s a quick overview of the Rainbow Shark. These facts will help you better grasp this unique fish and prepare you for the more in-depth discussions in the latter sections.

Order Cypriniformes
Family Cyprinidae
Genera Epalzeorhynchos
Size Four to six inches in length
Lifespan Five to eight years
Temperament Semi-aggressive and territorial
Color Light or dark body with bright red fins
Care Level Needed Low to moderate
Minimum Experience Level Needed Not recommended for beginners; best for experienced fishkeepers
Minimum Tank Size Required 50 gallons
General Community Behavior Capable of getting along with other freshwater fish species but may exhibit aggression

Origins of the Rainbow Shark

The Rainbow Shark was originally abundant in the warm waters of Southeast Asia. They could easily be found in the flowing rivers of Laos, Malaysia, Myanmar, and Thailand. The locals dubbed this amazing fish the Rainbow Shark due to its bright red fins that contrasted nicely with its slim, torpedo-shaped body. The Rainbow Shark also goes by the names Red Fin Shark and Ruby Shark.

How to take care of rainbow sharkWithin the scientific community, this territorial freshwater fish is known as the Epalzeorhynchos Frenatum. The name Epalzeorhynchos Frenatum is quite a mouthful but is thought to be a descriptive latin name that pertains to the Rainbow Shark’s head which has a small bump or protuberance. This fish is part of the cyprinid family, including relative species such as Barbs, Carps, and Minnows. Like other cyprinids, the Rainbow Shark has two barbels that extend a few centimeters above its mouth.


A full grown Rainbow Shark is known to reach lengths of a little over eight inches in the wild. However, in a home setting, Rainbow Sharks usually grow to about six inches long, with the largest ones reaching up to eight inches long similar to their cousins that thrive in their natural habitat. Typically, the female Rainbow Shark is rounder, thicker, and slightly bigger than the male Rainbow Shark. However, this will not be evident until the juvenile Rainbow Sharks reach their full maturity or until they reach sexual maturity.

Rainbow Sharks are quite popular among aquarists because of their beautifully contrasted scales. Some of these fish may have a dark brown or blue body with bright red fins, while other Rainbow Sharks might have a lighter colored body with a less intense but almost translucent shade of red for their fins. The light-colored version of this fish is often referred to as the Albino Rainbow Shark and is a favorite among fishkeepers who specialize in strange and rare fish.

Rainbow Shark Tank Setup 101

A large part of providing proper care for Rainbow Sharks comes in designing an aquarium that can make them feel comfortable and safe. At this point, you should note that the Rainbow Shark is usually raised on its own in a 50-gallon tank or with other fish species in a much larger aquarium. This notorious red-finned freshwater fish will not tolerate living in a small space with another Rainbow Shark at all. Forcing two or more Rainbow Sharks to live in the same 50-gallon tank will lead to unnecessary stress, increase the probability of territorial fights among your fish, and drastically shorten the typical Rainbow Shark lifespan.

With that said, here are some of the immediate tank water aspects you should plan for when setting up your Rainbow Shark tank.

Temperature 72 to 78 degrees Fahrenheit; the ideal temperature would be around 77 degrees Fahrenheit
pH Level 6.5 to 7.5pH
Water Hardness Level 5 to 11 dGH
Light Level  Low to Moderate

In addition to these water parameters, there are also other things you need to pay attention to when designing a suitable aquarium for your Rainbow Shark:

– Aquarium Size

It is crucial that you have enough space in your aquarium to house your Rainbow Shark properly. As a rule of thumb, you should aim to keep only one Rainbow Shark for every 50 gallons of aquarium capacity. This means that if you intend to keep more than one adult Rainbow Shark in the same tank, you need to have an aquarium with a capacity of 100 gallons or more.

The rest of your tank planning will also revolve primarily around how much space you have to work with and what other flora or fauna, if any, that you want to house with your Rainbow Shark.

– Substrate and Flora

When designing an ideal aquascape for Rainbow Sharks, you would do well to use sandy substrates and hardy flora. The best aquarium is one that mimics the natural habitat of the fish and aquatic plants that you want to care for. That said, Rainbow Sharks were most abundant in warm and flowing rivers with sandy bottoms. Selecting fine sand as the substrate of your aquarium will not only make your Rainbow Shark feel more at home, but it will also benefit you in that sand is relatively easy to clean and maintain.

As an alternative, you can also use fine gravel as the substrate of your aquarium if you cannot find any sandy substrate or if the majority of your tank inhabitants prefer a gravelly bottom layer over a sandy one.

In addition to choosing the right kind of substrate for your Rainbow Shark, you should also include aquatic flora in your aquarium if you do not already have them. Including aquatic plants such as Anubias, Java Fern, and Hornwort will make your aquarium more natural and inviting for your Rainbow Shark. The flora will also give your new fish places to hide, explore, or claim as its territory. You can also add small rock caves or wooden debris pieces to enhance your aquarium and make it feel more like a real river for your Rainbow Shark.

– Filtration, Temperature, and Light Levels

Another thing to think about before you bring home a Rainbow Shark or two is if your aquarium can handle a high level of filtration. Installing a strong filter in your tank will produce fast-flowing water, which is excellent for Rainbow Sharks as they are accustomed to this kind of environment. Your Rainbow Shark will also be more likely to thrive in an aquarium with consistently warm water temperature and a pH level that ranges from 6.5 to 7.5.

At the same time, you also need to look at the lighting system you have for your aquarium. Though Rainbow Sharks are not too sensitive to fluctuating light levels, you should still exercise care when increasing or decreasing your aquarium light’s intensity or length of exposure. Providing bright light for an extended period of time makes your aquarium prone to algae growth. This is not usually a problem for Rainbow Sharks as this type of fish eats algae as well as a whole host of other kinds of food. However, it is best to err on the side of caution as one Rainbow Shark cannot stand up to an explosion in the algae population in your tank.

Aim to keep low to moderate light levels in your aquarium, and ideally switch them on and off to mimic the natural day and night cycle.

Choosing the Best Red Fin Shark for Your Tank

Now that you know more about the Red Fin Shark, you probably want to add this freshwater gem to your aquarium. In this section, our experts share what they’ve learned about how to select the healthiest Red Fin Shark for your home tank.

– Bright Eyes and Alert Bodies

As with most fish, one of the most reliable signs of good health in a Rainbow Shark can be observed in its eyes. Choose a fish that has bright eyes that are free of any cloudiness, growths, or discoloration. Similarly, pay attention to the body shape and movement of your potential Rainbow Shark. The fish should not exhibit any signs of sluggishness or hindered movement.

– Clean Scales and Whole Fins

Next, observe the fish’s scales and fins. Be sure that your chosen Rainbow Shark has clean scales all over its body. There should be no dull-colored or crusty scales as these are early warning signs of a fungal infection. Check the fish’s fins and ensure that they do not have any tears, nips, or holes. This might be difficult as Rainbow Sharks are quite aggressive and may get into fights with other fish; however, it would be in your best interest to choose a fish with fins that are as intact and whole as possible.

– Graceful Movement and Active Behavior

If you are sourcing your Rainbow Shark from your local fish store, ask the storekeeper if you can drop a small amount of food in the tank. Use this opportunity to observe your chosen fish’s behavior when food is introduced and when it swims with other creatures that share its immediate environment. Is your chosen Rainbow Shark interested in the food at all? Did it fight with the other fish over the food you dropped?

Taking note of these behaviors and movements now will make it easier for you to plan your Rainbow Shark’s tankmates properly later on.

Care Guide for Rainbow Sharks

As mentioned earlier, the Rainbow Shark is not the easiest fish to keep because of its territoriality and low tolerance to other fish of the same species. It is, however, not so fussy when it comes to its diet and points for care. Experienced fish keepers who have handled aggressive cichlids or delicate nano fish should be well-poised to care for the beautiful Rainbow Shark as long as they keep the following points in mind.

– Diet and Food Basics

Rainbow Sharks are omnivores. Unlike fish that eat only meat or plant matter, Rainbow Sharks thrive on a diet that contains both food types and other supplements. Here are some of the best types of food to include in your Rainbow Shark’s diet:

Fish Flakes and Pellets

Rainbow Sharks are not picky eaters. They will often dive for any food material that sinks to the bottom of your aquarium. That said, you should include high-quality fish flakes or pellets as a relatively large part of your Rainbow Shark’s diet.

Frozen Meaty Food

While Rainbow Sharks sometimes hunt down insects and larvae in the wild, they are not typically classified as hunters or predators. They need sources of protein to grow and remain healthy, but they will not prey on small aquatic creatures as other fishes might. In that regard, your best bet is to include frozen food in your Rainbow Shark’s diet. Frozen bloodworms, insects, larvae, and crustaceans make for a great starting point and will give your Rainbow Sharks the protein and minerals they need to thrive.

Plants and Vegetables

You should also make it a point to occasionally feed your Rainbow Shark with a variety of plants and vegetables. This will help round out their diet and prevent them from bloating or being overfed. Some vegetables you can feed your Rainbow Shark are cut-up cucumber, spinach, lettuce, and peas.

A Note on Algae

Rainbow shark food requirementsRainbow Sharks also actively feed on algae. They help in controlling the algae population of an aquarium but do note that they will not survive on this food source alone. If you are housing other fish in your aquarium, it would be best to prevent algae blooms from getting out of hand at all as this could negatively impact your tank’s water quality.

Feed your Rainbow Sharks once daily only. This will help them keep a lean body and a normal weight. Obese Rainbow Sharks are not only prone to diseases and movement difficulties, but they also tend to become some of the meanest fish in the tank, bullying smaller fish that happen to trespass in their territory.

– Common Illnesses and How To Treat Them

Though the Rainbow Shark is not a highly sensitive or delicate freshwater fish, it can still catch common fish illnesses. Below are some of the most common health conditions that Rainbow Sharks are known to suffer from and how to treat them.


Rainbow Sharks are avid eaters. This makes them prone to digestive tract illnesses such as bloat. Bloat occurs when there is an accumulation of gas or food solids in the digestive tract for an extended period of time. It’s easy to know if your Rainbow Shark has Bloat because you’ll notice that it has a distended or balloon-like lower belly and that it is swimming in a strange way.

If you suspect your Rainbow Shark has bloat, then you may want to gently move it into a quarantine tank. This will help you control its food intake more, and it will also be an environment where there is less stress for your fish. You can also treat Bloat using over-the-counter medicines like Erythromycin or Doxycycline.

– Constipation

Rainbow Sharks are also prone to constipation. The signs to watch out for in this case include the following: sluggish movement, loss of appetite, and a swollen but not distended belly.

You can treat constipation by feeding different types of food to your fish to help the waste pass naturally. For omnivores like your Rainbow Shark, you can try feeding brine shrimp or even live daphnia. These will help ease the digestive tract of your constipated fish.


Also known as the White Spot Disease, Ich is an indicator of poor water quality. As its name suggests, the main symptom of Ich is a white spot that forms on the head or body of an infected fish. If you suspect that your Rainbow Shark has Ich, it would be prudent to increase the frequency of your water changes. You can also purchase chemical treatments for Ich at your local fish store.

Finding Tank Mates for Your Rainbow Shark

Because of its territoriality and bouts of aggression, the Rainbow Shark is not the easiest fish to house with other aquatic creatures. However, if you are determined to care for this fish in a community tank, there are some types of fish that would be able to hold their own against this feisty freshwater terror.

– Tetras

Rainbow Sharks are bottom-dwellers. This means that they will be less likely to bother fish that occupy the upper and middle layers of the aquarium. In this regard, pairing your Rainbow Shark with peaceful Tetras is a good way to go.

Some of the best Tetras that can serve as neighbors for your Rainbow Shark include the Buenos Aires Tetra, Congo Tetra, and the Diamond Tetra. These are all schooling fish. Be sure to stock at least eight or more of them in the same tank as your Rainbow Shark to prevent any episodes of territoriality or aggression.

– Plecos

The peaceful Plecos is another good match for your Rainbow Shark. Though Plecos are also bottom-dwellers, most species are large enough that your Rainbow Shark will be unlikely to get on its bad side. Choose Plecos that grow to about the same size as your Rainbow Shark. One example of a good Plecos neighbor would be the Bristlenose Plecos.

As long as you are capable of providing enough room for these two types of fish, you should have no trouble housing your Rainbow Shark with these substrate giants.

– Danios

Lastly, we recommend the docile Danios to share the same space as your Rainbow Shark. Just be sure to choose a Danios fish that can grow to more than half of your Rainbow Shark’s length, and have six or more of them in your tank. This should be enough to deter your Rainbow Shark from picking on them or pestering them over territory. The beautiful Zebra Danio is one of the most common Danios that aquarists have successfully housed with a Rainbow Shark.

Notes on Breeding Rainbow Sharks

At this point, you might be wondering about how to breed Rainbow Sharks in captivity. Many experienced aquarists have asked the same question. However, the short answer to this is that it is extremely difficult and technically impossible to breed Rainbow Sharks in a home aquarium setting. This is mostly due to the Rainbow Shark’s non-tolerance to living with the same species in a closed environment.

Rainbow Sharks are egg-layers. During mating season, the male Rainbow Shark’s fins will change to a more intense red. In the wild, a pregnant Rainbow Shark will scatter her eggs on a plant or soft surface. The male Rainbow Shark will then need to fertilize these eggs. The Rainbow Shark does not exhibit any paternal or maternal behavior, so the eggs are left on their own to hatch.

This would be very problematic in an aquarium setup as Rainbow Sharks, regardless of sex, are highly aggressive towards each other. The fertilization of the eggs will be extremely difficult, and even if a clutch of eggs are successfully fertilized, the juvenile Rainbow Sharks will be under a lot of stress just to survive. As such, breeding Rainbow Sharks in a home aquarium has not been encouraged by the majority of the fishkeeping community.


Rainbow shark water requirementsWe covered a lot of topics about the Rainbow Shark in this article. Here are the most important points of our discussion for your reference:

  • The Rainbow Shark is a tropical fish that hails from the rivers of Southeast Asia.
  • This fish is highly aggressive towards its own species and quite territorial as well.
  • The Rainbow Shark needs a lot of aquarium space; 50 gallons to 1 Rainbow Shark is a good rule of thumb to follow.
  • Rainbow Sharks are omnivores and will thrive on a balanced diet of pellets, frozen food, and cut-up vegetables.
  • They can be housed in a large community tank with Tetras, Plecos, and Danios, among other types of peaceful fish.

Now that you know all of these facts about the feisty Rainbow Shark, you should be well-equipped to introduce one into your home aquarium and care for it with confidence.

5/5 - (27 votes)


Please enter your comment!
Please enter your name here