Full Guide on Caring for a Rainbow Shark

Many people look for uniqueness when getting aquarium fish. The rainbow shark is a stark definition of uniqueness, with a blue, slightly slender body and reddish fins, which explains its other name, the redfin shark.

There is plenty to know about this fish if you are interested in keeping it. Read on for in-depth information about its origin, care requirements, breeding, and ideal tank mates. At the end of this piece, you will be able to determine whether it is a worthy housemate.

Scientific Classification

Scientific Name: Epalzeorhynchos frenatumCommon Names: ruby shark, redfin shark, red-finned rainbow shark minnow, whitefin shark
Genus: epalzeorhynchos
Family: Cyprinidae

History and First Sighting

Contrary to its name, the rainbow shark is not a shark but belongs to the ray-finned fish category. It originates from Southeast Asia, particularly the Mekong, Xe Bangfai, and Chao Phraya basins. It is a freshwater fish that prefers the warm waters of the mentioned basins. Its natural habitat also features sandy bottoms rich in algae and plankton.

Usually, rainbow sharks move to flooded areas during the monsoon season but retreat downstream when flooding ceases. While classified as the least concern, their numbers in the wild gradually depreciate. Scientists believe the dwindling numbers are due to the interruption of their natural habitat, primarily due to dam construction on some rivers.

The good news is that the pet trade does not affect the wild populations of the rainbow shark. Most of the aquatic pets come from fish farms in Southeast Asia.

Species Overview


The rainbow shark belongs to the epalzeorhynchos genus, also referred to as the freshwater shark genus. Freshwater sharks belong to the Cyprinidae family, while true sharks are members of the Chondrichthyes family.

The red-finned shark is a bottom and middle-level dweller in the fish tank. It is an excellent cleaner due to its feeding habits – the fish eats leftovers and algae growing in the tank.

Several aquarium hobbyists say the rainbow shark is not ideal for beginners. Keeping them needs some expertise, and they may frustrate novices.

Rainbow Sharks Lifespan

The rainbow shark can live between 5-7 years with excellent care, though some can push the limit to 8 years. You must ensure that the fish feeds well and resides comfortably to lengthen its lifespan. They live longer in the wild, with most individuals clocking eight years.

The Appearance of Rainbow Sharks

As hinted earlier, the rainbow shark owes its growing popularity to its unique appearance. Let us look at various aspects of this freshwater shark’s looks.

Distinct Features (Colors, Patterns, Fins)

At first sight, you may think that the rainbow shark is a juvenile shark or a small member of the shark family. It has a slender body, typically black, grey, or a lighter or darker shade of blue. A prominent dorsal fin sticks out due to its orange or red hue. The fin is the reason many people liken the fish to sharks.

The other fins are also reddish-orange and may have a darker base. The dorsal fin may have around 11 branched rays. This fish has a forked tailfin.

The face appears rounded, with deep-set eyes on either side and a rounded mouth. Another distinct feature of the rainbow shark is the dark stripe on its face, extending slightly past its eyes.


The redfin shark grows up to 6 inches, mostly in the wild. In captivity, they are shorter, with most individuals growing to 4 inches, though some can reach 6 inches. In rare instances, this freshwater shark will grow up to 8 inches.

The Albino Rainbow Shark

The albino rainbow shark is highly sort after due to its distinct appearance. It has a white body, which some people describe as slightly translucent. The fins retain the orange-red hue. The eyes are also red.

Albino redfins are very rare and costly.

How to Take Care of Rainbow Sharks

Taking care of rainbow sharks can be quite challenging for those keeping fish as pets for the first time. It will be a walk in the park if you have experience with pet fish.

You must develop a care routine for your rainbow sharks to thrive. The following are the crucial elements of caring for your aquatic housemate.

Food and Diet

Redfin sharks are omnivores. In their native habitat, they feed on algae, decomposing plants, zooplankton, freshwater insects, and their larvae. They also eat crustaceans like shrimp. The diverse diet ensures they get all the essential nutrients.

When keeping it in an aquarium, you should abide by the ruby shark’s omnivorous diet. As this fish resides in the bottom and middle surfaces of the tank, you should feed them food that sinks, such as sinking food pellets or algae tablets. You may also offer the fish veggies such as lettuce, zucchini, spinach, and peas.

Rainbow sharks need protein for healthy growth and for their coloration. Throw in some live shrimp or other crustaceans that they can hunt down. Bloodworms, live aquatic insects, and zooplankton are other protein-dense foods suitable for the freshwater shark.

You should feed the fish three times a day. As they are bottom feeders, they do an excellent job of dealing with leftovers that sink to the bottom of the aquarium.

Please note that while this Southeast Asia original fancies algae in the wild, it is not a proficient algae cleaner. It mostly prefers algae flakes in captivity.

The Right Tank Size

The rainbow shark is very territorial and needs a large tank. A 50-gallon tank is the least you can go for this freshwater bottom feeder. The tank size should be bigger if it houses other fish.

Furthermore, the tank should be broader and longer to give the fish the illusion of vast space. A small space may quickly dampen its mood and trigger its aggression. Accessorize the tank with caves, rocks, and plants, which are excellent hiding spots.


Regular LED aquarium lights work fine in a redfin shark’s tank. The lights decorate the aquarium and help highlight the fish’s colors. Pick programmable lights to get a natural day and night cycle.

Water Flow

Fast-flowing waters characterize the red-finned shark’s native habitat. You should mimic the water current by installing a powerful filter. You may install more than one filter for optimum water flow.

Recommended Water Parameters

Many aquarium hobbyists mess up on water parameters and shorten the lifespan of their pet fish. While ruby sharks are hardy and can adapt to various environments, they can suffer when the water parameters vary beyond their survival point.

The following are the values to remember when keeping this fish as a pet.

  • Water temperature: 72-82° Fahrenheit, ideally 77° Fahrenheit
  • Water pH: 6.5 to 7.5
  • Hardness: 11dGH

You must invest in a water heater to keep the temperatures constant. Fluctuating heat levels will stress the fish and affect its health in the long run. Moreover, the water should be fresh and well-oxygenated. A bubbler will come in handy for oxygenation.

Change 25% of the water at least once weekly for the freshwater fish to thrive.

What Do Rainbow Sharks Need in Their Tank?

Once you get your fish tank, you must prepare it for its occupant. Start by getting a suitable substrate. Soft gravel or sand is ideal. Avoid sharp gravels as they may injure the bottom feeder as it looks for food. Put water in the tank and treat it before introducing the fish.

The tank should not be plain, especially if it houses several individuals, as they may get into fights. Add caves, driftwood, rocks, and plants to the tank. Pro aquarists recommend hard-leaved plants, like anubias, hornwort, Java fern, and Amazon sword, for a red-finned shark’s aquarium.

Be moderate with the accessories, especially the plants, as you may interfere with the tank’s current flow.

Filter System

As mentioned earlier, a filter is a must-have in the redfin’s tanks for current flow. Apart from ensuring water flow, the filter also helps with waste management. The circulating water passes through a sponge chamber in the filter, which traps physical matter. The next section contains bio media, which eliminates harmful chemicals.

You may use several filters to achieve the desired water flow. Check the filter’s rating, expressed in gallons per hour (GPH). The GPH should be high for the perfect water flow for the ruby shark. Ideally, the filter rating must be four times the tank size. If you have a 50-gallon aquarium, the filter’s rating should be around 200 GPH.

You can get a powerhead, air stones, and wavemakers to boost the filter’s water circulation power. Additionally, you may create space in the tank by reducing plants and rocks, which may affect water flow.

Common Potential Diseases

The rainbow shark is hardy but occasionally goes down with various ailments. The good news is that most of these diseases are treatable. Moreover, you can avoid the conditions if the fish has a balanced diet and lives in a clean aquarium.

Let us look at the common potential diseases that affect the ruby shark.

Rainbow Shark Disease

The rainbow shark disease is not an actual disease but rather a stress response by the fish to rapidly changing water parameters. An out-of-balance nitrogen cycle is the primary culprit behind the stress. This may be due to leftover food or excess waste production.

Avoid overfeeding your fish, and clean leftover food to maintain the nitrogen cycle balance.


Ich or white spot disease is a common parasitic condition that affects freshwater fish. The main sign of ich is discomfort, whereby affected fish tend to scratch themselves against rocks and other objects in the tank. Later, the skin will develop white spots.

Other signs of ich are:

  • Loss of balance and upside-down swimming
  • Inactivity and lethargy
  • Loss of appetite
  • Discoloration

The condition may lead to secondary bacterial and fungal infection, as scratching causes wounds, which are pathways of the disease-causing microorganisms. You should treat your fish immediately after you notice the signs, as itch has a high mortality rate.

You manage the disease by medicating the tank’s water and increasing the temperature to around 89° to hasten the parasites’ life cycle. Prevention involves maintaining high hygiene standards in the fish tank. Clean decorations, like rocks from the river, before introducing them into the aquarium.

Swim Bladder Disease

Odd swimming, trouble keeping upright, and sinking to the bottom are likely pointers of swim bladder disease. The disorder is non-contagious, and your fish may get it due to mechanical, physical, and environmental agents. Inbreeding is another possible cause.

Ruby sharks may contract swim bladder disease due to intestinal parasites and constipation. Treatment is quite challenging, as the cause may not be clear. Your pet doctor may offer peas to affected fish if constipation is the root of the problem. Other times, minor surgery to remove part of the swim bladder may alleviate the situation.

To prevent the disease, feed your fish adequate food to avoid constipation, and ensure the tank is always clean.


Fish, too, can get bloated, which you notice from their expanded stomachs. The fish may be uncomfortable and will avoid moving. Probable causes of this illness are internal bacterial infections, intestinal blockage, intestinal growth, and constipation.

Peas will help with constipation, and antibacterial medications will combat bacterial infections. Your vet needs to check up on the ruby shark for the correct diagnosis.

Behavior and Temperament


The rainbow shark is not an excellent choice if you are looking for a peaceful aquatic housemate. It is famous for its aggression, which is surprising considering how calm it is in the wild.

In their native habitats, rainbow sharks are cordial with each other and rarely engage in fights. However, things take a dive when in captivity. The possible explanation is that their native home is large, allowing them to thrive in their territories without crossing paths.

Despite being small-bodied, this freshwater fish can fiercely fight. The good news is that they are not big enough to attack humans.

Experienced aquarists advise against keeping two or more redfin sharks in a small tank. Their territorial nature kicks in, and they will get into a head-butting or tail-fighting contest, which may lead to biting. Bigger individuals bully smaller ones and will engage in a chase all over the tank.

The situation may result in death, either due to injuries or stress. The aggression of this red-finned bottom eater is also noticeable with other species, especially if they are smaller. You must consider the temperament of these fish tank bullies before introducing a tank mate.

Rainbow sharks are not typically nocturnal, but they emerge from their hideouts to swim around when it is dark.

Best Tank Mates

We now know that ruby sharks are not the best tank mates for smaller fish species. You should house them with slightly larger middle and upper-level feeders. They are less likely to fight with such tank mates as they occupy different levels.

Zebra danios are excellent tank mates. They are dither fish, meaning they swim at the upper levels of the aquarium. They are popular among aquarists, as they help calm temperamental fish, like the red-finned shark. Zebra danios are schooling fish, so you should keep at least five in a tank.

Black skirt tetras are renowned for being great aquarium mates with aggressive and semi-aggressive fish. They are middle-water dwellers and also love hiding behind rocks and vegetation.

Rainbow sharks can also get along fine with rainbowfish. There are more than ten species of rainbowfish, and they are all shoaling fish, meaning you must keep them as a group of around five or six in a tank.

The following are other potential tank mates of the rainbow shark.

  • Bee shrimp
  • White cloud mountain minnows
  • Congo tetra
  • Hillstream loach
  • Cherry barb
  • Rasboras

Guppies and rainbow sharks won’t get along, as the former are smaller. Also, guppies are livebearers, and the rainbow shark may prey on their fry. Add African cichlids, cory, gouramis, and other freshwater sharks to that list.

Onto the same species, keeping two or more rainbow sharks in one tank is not a good idea, as they will likely engage in territorial fights. If you decide to have them share a tank, you should get a bigger one. A 125-gallon tank can hold 2-3 individuals. Additionally, you must provide hiding spots like caves and vegetation.

Rainbow Sharks Breeding

In their native habitat, ruby sharks breed around October and November. The females will lay eggs depending on the length of the day and temperature. The males will fertilize the eggs by spraying milt on them. The eggs hatch a week later, and the fry can swim. They will reach full maturity after a year.

Gender Differences between Rainbow Sharks

Red-finned sharks exhibit sexual dimorphism, though the gender differences may be too subtle to notice. Males are typically slenderer than females. Male ruby sharks also have a brighter coloration, and a prominent anal fin, and the tail fin has black outlines.

How to Breed Rainbow Sharks

Breeding rainbow sharks in captivity is very challenging. First, these freshwater sharks prefer breeding in riverine conditions, which are hard to replicate in an aquarium. The fish are also aggressive, which makes breeding almost impossible.

The female fish may lay eggs, but the males will hardly fertilize them. Nevertheless, there are fish farms that successfully breed rainbow sharks for the pet trade.

The following are steps for breeding rainbow sharks in captivity.

  1. Set up a separate tank for breeding. The breeding tank should be at least 75 gallons and have aquarium-grade substrate at the bottom.
  2. Fill the tank with fresh water.
  3. Pour liquid dechlorinator into the tank according to the indicated dosage. This substance eliminates harmful impurities from the water.
  4. Place rocks and other accessories in the tank. As you know, the ruby shark is territorial and aggressive. If the aggression becomes too much, one of the sharks needs a place to hide.
  5. Install the heater and set the temperature between 72° and 82° Fahrenheit. Install the filter and let it run for 48 hours for a clean environment.
  6. Introduce a male and female ruby shark into the breeding tank. They should be sexually mature: matured sharks are at least 4 inches long. You now wait and see how the fish get along. Separate them if they are antagonistic toward each other.
  7. If there are no conflicts between the fish, you should provide them with a high-protein diet to stimulate breeding. Feed them brine shrimp and tuna and change 25% of the water daily.
    Your attempts will be a success if the freshwater sharks rub against each other, leading to the female laying eggs. The male will spray milt on the eggs to fertilize them.
  8. Establish a 20-gallon fry tank using dechlorinated water and a heater. Use an air stone for water circulation.
  9. Carefully transfer the eggs from the breeding tank to the fry tank, where they will hatch 5-7 days after fertilization.

Caring For Rainbow Shark Fry

After they hatch, the fry will feed on the yolk sac. Introduce them to liquid fry food once they eat all the yolk. Stick to liquid food for two weeks before you bring in baby brine shrimp. Continue monitoring them and shift them to their separate tanks when they reach a length of 1 inch. You now feed them adult food.

Final Thoughts

A Rainbow shark is a popular aquatic pet that you may consider due to its striking looks and hardiness. While it looks impressive, it is quite stubborn and doesn’t get along well with various tank mates, including members of its species.

This piece provides us with the necessary information about the rainbow shark, including how to take care of it. If you decide to get this freshwater shark as your pet, you must ensure high hygiene standards for its well-being. Additionally, ensure you feed it well and pair it with suitable tank mates.