Rainbow Shark: Care, Size, Tank Mates, Tank Size & Food

Common Name(s)Rainbow Shark
Scientific NameEpalzeorhynchos frenatum
OriginSoutheast Asia
Temperature75-80°F (24-27°C)
Size6 inches (15 cm)
Minimum Tank Size55 gallons
Food & DietOmnivorous bottom feeders
Lifespan8 years
Water pH6.0-8.0
Tank MatesAvoid or stock other bottom dwellers with caution
BreedingBreeding pair spawns around October to November, but they are considered difficult to breed.
DiseaseMay be suseptible to constipation, Dropsy, and Ich.
Rainbow Shark
Rainbow Shark (Epalzeorhynchos frenatum)

Despite their name, Rainbow Sharks are not related to true sharks, rather this freshwater “shark” is an actinopterygiian (“ray-finned fish”) that earned the name because of its shark-like appearance, which includes a triangular dorsal fin on top. Rainbow Shark have various nicknames, for example: Ruby Shark, Red-fin Shark, Red-finned shark, Rainbow Sharkminnow, Green Fringelip Labeo, Whitefin Whark and Whitetail Sharkminnow. They are closely related to goldfish and carps, but their population is currently dwindling because of habitat destruction and fishing. Native to the warm Indochinese rivers of Mekong, Chao Phraya, Xe Bangfai and Maeklong, this species is physically capable of slow laps, as well as imposing bursts of speed, typical when capturing prey. Their brightly coloured red/orange fins stand out against their iridescent grey/brown/black body, which have rightfully earned them the ‘rainbow’ in their name.

Rainbow Shark Care 

Rainbow Sharks are both beautiful and riveting to observe, making them a very popular choice for aquarists to purchase. However, this species comes with its challenges due to its temperament and sensitivity to parameter spikes, therefore they are recommended for more advanced fish keepers that don’t shy away from doing their research. Rainbow Sharks must have premium water quality for optimum health, which means using regular testing kits and keeping a vigilant eye on the water parameters. This can be daunting for beginner aquarists who might not be aware of the dangers of over-feeding Rainbow Sharks. Often Rainbow Sharks are sold as “algae-eaters”, despite the fact that they consume less algae compared to Pleco, Amano Shrimp, and catfish. Rainbow Sharks will graze on algae, however, they are herbivorous and omnivorous eaters that require other food sources, such as invertebrates. Nevertheless, Rainbow Sharks have remained a favourite for decades and continue to dazzle fish keepers.

Rainbow Shark Temperature

Rainbow Sharks thrive in tropical climates and their benthopelagic characteristics means that their ideal temperature range is between 75°F to 80°F (24°C to 27°C). A heater may be necessary for fish keepers to install in order to ensure the temperature does not drop, unless the room is exceptionally warm.

Rainbow Shark Water Parameters

Rainbow Sharks are incredibly sensitive and aquarists must be vigilant when it comes to ensuring their water quality remains superb. This species can easily become distressed if water parameters drop or spike without warning, making the Rainbow Shark even more aggressive, which can be a problem if it lives in a community tank. Rainbow Sharks need well-oxygenated, soft water that mimics its native habitat, therefore a hardness level of 3 to 14 dKH is ideal. As a general rule, a pH between 6 to 8 is best, however hobbyists should aim for the middle of this range. Ammonia and Nitrite levels must be kept at 0 ppm, because even 2ppm can cause disease and stress for Rainbow Sharks. Nitrate levels should never exceed 20ppm. Their water ought to remain clean, with weekly cycles of 20% to 30%.

Rainbow Shark Size

Rainbow Sharks can grow up to a maximum size of 6 inches (15 cm) when they reach maturity, although the average purchase size is typically 1 to 2 inches (2.5 to 5cm). Rainbow Sharks can grow especially fast in the first year, and between 2 to 4 weeks they grow 0.5 to 1 inch (1.3 to 2.5 cm). However, it can take months for this species to reach their full size.

Rainbow Shark Tank Size

Rainbow sharks require a minimum tank size of 55 gallons. If multiple fish are being kept in the same tank, a larger tank size is recommended. These fish require adequate space since they can have a semi-aggressive temperament and can become very territorial.

As territorial fish that spend most of their time near the bottom of the tank, the dimension of the tank is important as well. Aquarium tanks that are long and wide provide more space for the fish than tall tanks that have a narrow shape.

In addition to the tank size and shape, the tank should have hardscape such as rocks, driftwood, and caves. These structures can help them establish their territories within the tank. It can also help break the line of sight, providing the illusion of a larger tank to the fish.

Rainbow Shark Food & Diet

Rainbow Sharks are omnivorous bottom feeders that eat almost any variety of food, which helps to keep their striking colouration bright and pigmented. Because they are benthopelagic, their meals need to sink to the base of the aquarium and last maximum 5 minutes, otherwise there is a risk of over-feeding. Feeding can take place two to three times a day and any uneaten food must be removed. Food in the form of pellets, flakes and algae wafers can be a good choice.

Rainbow Sharks will graze on algae, spirulina, periphyton, phytoplankton, and zooplankton. Lightly blanched vegetables that have cooled down are a good food source, including celery, carrots, zucchini, peas, and spinach. Rainbow Sharks can eat raw vegetables such as: lettuce, beet tops, and swiss chard. Small crustaceans and insect are an excellent source of protein, for example: brine shrimp, blood worms, mosquito larvae, tubifex worms, daphnias, artemias, and aquatic insects.

Rainbow Shark Lifespan

In the wild, Rainbow Sharks can live up to 8 years, but in captivity this species will typically live 4 to 6 years. Generally, it is only with outstanding care that Rainbow Sharks will live past 4 years, as they are extremely intolerant of any water spikes and poor conditions.

Rainbow Shark Care Guide – My Favorite Community Fish

Rainbow Shark Tank Mates

Rainbow Sharks are partial to spending a lot of time at the bottom of the tank, and will even claim certain spots for themselves, chasing away anyone that comes too close. Fish keepers need to be very careful when picking tank mates for this species because of their behavioral quirks. Other bottom-dwelling species such as catfish should be avoided – instead fish that occupy the middle and upper levels of the tank would be more ideal. Species of similar or larger size, that have a semi-aggressive temperament would be able to tolerate the Rainbow Shark’s ‘annoying’ habits of intimidating other fish. It is best to avoid fish that look similar to Rainbow Sharks (e.g. Red Tail Sharks and Bala Sharks) as they will terrorize each other to death. It is best practice place the Rainbow Shark last in the tank, which will impede any attempts of trying to claim the entire tank as its own possession and should minimize some of that hostility.

Compatible tank mates include: Gouramis, Garbs, Danios, larger Rainbowfish, medium-sized Cichlids, Chromobita, Harlequin Rasboras, Botia, Syncrossus, True loaches (Cobitidae), and Yasuhikotakia genera.

Are Rainbow Sharks Aggressive?

Juvenile Rainbow Sharks start off as very withdrawn, hiding away in plants or caves and generally do well in groups. This behavior may mislead fish keepers into thinking they will remain placid forever. However, aggression increases as the Rainbow Shark grows, and this territory-obsessed fish will begin brawling and biting each other. It is wise to keep Rainbow Sharks in separate aquariums, as there is always a high probability they will clash when confronted with each other’s presence.

Rainbow Shark and Angelfish

It is best to avoid keeping Rainbow Sharks and Angelfish in the same tank, as Rainbow Sharks have a reputation for aggression and territorial behaviour. Angelfish have characteristically long dorsal and anal fins, with two elongated ventral fins that the Rainbow Shark might nip at. They are not compatible as tank mates.

Rainbow Shark and Cichlids

Aquarists can keep Rainbow Sharks with specific Cichlids that are of similar temperament and size or slightly larger. Aggressive or semi-aggressive Cichlids will defend themselves and stand up to Rainbow Sharks if they attempt to disturb the other, making it possible for the two to co-exist without any serious issues. The firemouth cichlid (Thorichthys meeki) can be a great choice, and aquarists can keep them in a school or a pair. The tank must be large enough with enough hiding places and swimming space at the top for the Rainbow Shark to dart about. A pH of 7.5 is ideal for both species, who also prefer hard water.

Rainbow Shark and Betta fish

Betta fish and Rainbow Sharks are incompatible for several reasons. The size of a Betta fish is far too small, making it vulnerable to the Rainbow Sharks terrorising habits. Betta fish swim slower compared to Rainbow Sharks, so if a chase ensues, it will not be able to out swim the other, and the shark will try to eat the Betta’s fins.

Rainbow Shark and Goldfish

Rainbow Sharks and Goldfish belong to the same family (Cyprinidae), but that does not instantly make the two compatible. In fact, it is very difficult to keep these two in the same tank, even with certain precautions taken. The two species have different water temperature differences, their temperaments do not mix well, and preparing an aquarium large enough with the proper setup can be costly and might not even work in the end. Rainbow Sharks are belligerent, thus even if a hobbyist chooses Fancy Goldfish, which prefers warmer temperatures similar to that of Rainbow Sharks, it is likely to be bullied and chased around.

Rainbow Shark and Guppies

Guppies do not grow beyond 2 inches (5.1 cm), making them extremely vulnerable in the presence of a Rainbow Shark, who will not hesitate to bite the smaller fish. Without a tight lid on the aquarium, guppies are at risk of jumping out when attempting to escape from larger fish chasing them. Thus, these two species must not be kept in the same tank as they are incompatible.

Rainbow Shark and Neon Tetras

Neon Tetra’s are small fish, reaching only 2.5 inches (6.4 cm) and possess exceptionally peaceful temperaments, making them incompatible with the grumpier, territorial Rainbow Shark, who will terrorise the smaller fish. These two species should be kept in separate tanks for the sake of the Tetra’s safety.

Rainbow Shark Tank Setup

Rainbow Sharks need an adequate amount of horizontal space, therefore a rectangular aquarium will do best with an attached Hang on Back (HOB) filter. This will generate a much-desired current (Gallons Per Hour) 4 to 5 times the volume of the tank, as well as keep the water clean. Rainbow Sharks are found at the bottom of fast-flowing well-oxygenated freshwater rivers/streams with sandy bottoms, migrating seasonally into floodplains and returning only when the floods have dried up. Once purchasing a large enough aquarium, it is imperative that aquarists fit a tight lid on top, as this active species can jump out without warning.

Soft sandy substrate or fine pebbles is best for this bottom-dwelling fish, because anything hard or sharp may cut them when they start dashing around the tank in an excitable frenzy. Rainbow Sharks are territorial and must have several hiding places they can retreat to, such as hollow caves/logs, driftwood snarls, rocks formations, and dense living or artificial vegetation/plants. Hard-leaved aquatic plants will discourage sharks from nibbling on them, options include: Anubias, Amazon sword, Hornwort, Java fern, Lemon bacon, and Vallisneria.

Rainbow Shark Breeding

Breeding Rainbow Sharks in captivity is incredibly difficult and there are few reports of actual spawning taking place in a tank setting. Majority of Rainbow Sharks are bred in Southeast Asian commercial farms that will administer hormone injections to ensure successful spawning. The juveniles are then traded or sold to pet shops. Sexual dimorphism is present in this species once they have reached sexual maturity (4 inches, 10 cm), with males displaying more vibrant pigmentation compared to its female counterparts. Males are also typically more slender during breeding season (October to November) and possess black streaks along their tail fins.

Spawning Rainbow Shark is no easy task, and their antagonistic personalities means that they will fight each other relentlessly. If there is an inclination that a couple is ready to mate, they will rub against one another, where afterwards the female will deposit her eggs on the sandy substrate, with the males fertilizing them by releasing his milt. The eggs, which are clear and hard to the touch, need at least a week to hatch, where they will happily eat their yolk sac for a few days. It takes three weeks for juveniles to grow large enough to be able to join a community tank. Be warned that Rainbow Sharks will try to attack and eat their own fry, so separating them would be preferred.

Rainbow Shark Disease

If conditions in the tank are unsuitable, Rainbow Sharks may develop health complications that can be life-threatening. Common illnesses to watch out for include: Constipation (not enough fibre in diet), Dropsy/Bloat (overfeeding, hexamita, viral/bacterial infection, etc), and Ichthyophthirius multifiliis (parasitic infection). These diseases are common with most aquatic pets and fish keepers are able to treat them on their own. Rainbow Sharks were discovered to be vulnerable to Betanodavirus in the wild, a pathogen which causes viral nervous necrosis, with no available treatment.

Antibiotics, such as Prazipro are a safe to use, but medications containing copper, salt, dyes should be avoided. Isolating ill Rainbow Sharks in their own tank is recommended, as it will not only prevent spread of infection, but keep other fish safe due to the increase of aggression present.

Where Can I Find Rainbow Shark for Sale?

Most online fish stores and local pet shops stock juvenile Rainbow Sharks for $3 to $4 due to their popularity, though sometimes there are discounts for purchasing an entire group. While this fish is readily available and inexpensive, a hobbyist may find its tank setup is quite pricey because of how much space they require. They are also sensitive in captivity, so testing kits must be purchased to monitor water conditions. 

Rainbow Shark and Albino Rainbow Shark

Albino Rainbow Sharks (also known as albino rainbow sharkminnow) is a variety of Rainbow Shark, with the same red fins, but has been genetically modified to have a white body. Its temperament and biology is identical to its more pigmented counterpart – the only existing difference between the two is the colouration.  Albino Rainbow Sharks are often mistakes for Redfin Sharks (Epalzeorhynchos munense) and despite the similarities in appearance, they are in fact different species.

Rainbow Shark and Bala Shark

Rainbow Sharks and Bala Sharks (Balantiocheilos melanopterus) come from the same family of Cyprinidae, but that is where their similarities end. This species has a nervous disposition and does best in schools, compared to Rainbow Sharks who appreciate their solitude. Any sudden movement may trigger the Bala Shark to dart anxiously about, even jumping out of the tank if there is no lid present. Bala Sharks, also known as Tricolor Shark, Tricolor Sharkminnow, Silver Bala, Silver Shark, or Shark Minnow, are generally bigger in size (8 inches, 20 cm) and have a silver/grey body with black markings on their dorsal, caudal, anal, and pelvic fins. Bala Sharks have a peaceful temperament and make great community fish, although they may be bullied by more aggressive species, such as Rainbow Sharks.

Rainbow Shark and Red Tail Shark

Red Tail Sharks (Epalzeorhynchos bicolor), also known as Red-Tailed Black Shark, Red Tail Labeo, Fire Tail Shark, and Red Tail Shark Minnow are native to Thailand, currently endangered in the wild, yet remain popular among fish keepers due to their striking appearance. Red Tail Sharks are similar in size to Rainbow Sharks, belonging in the same family (Cyprinidae) and are often confused with one another. Red Tail Sharks are black all-over, except for their caudal fin which shifts to a vibrant red colour, separating the colours with a sudden vertical stripe. Putting these two in a tank would be a mistake, because of their aggressive tendencies and there would no doubt be a fight to the death. 

Fish Laboratory

With decades of collective fishkeeping experience, we are happy to share the fish care tips that we've picked up along the way. Our goal at Fish Laboratory is to keep publishing accurate content to help fishkeepers keep their fish and aquarium healthy.

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