HomeAquarium FishRainbow Shark - Size, Tank Mates, Price, Breeding, & More!

Rainbow Shark – Size, Tank Mates, Price, Breeding, & More!

The Rainbow Shark (Epalzeorhynchos frenatum) is a well-liked fish for aquarium enthusiasts due to its resemblance to a shark. Although not an actual shark, it’s triangular dorsal fin and body shape give it a similar appearance.

Classified as actinopterygian, or “ray-finned fish,” Rainbow Sharks are unexpectedly related to goldfish and carp. In contrast, real sharks belong to the Chondrichthyes lineage, referred to as “cartilaginous fishes.”

Regrettably, their wild populations are declining due to habitat destruction and fishing. These fish originate from the warm Indochinese rivers of Mekong, Chao Phraya, Xe Bangfai, and Maeklong.

OriginSoutheast Asia
Scientific NameEpalzeorhynchos frenatum
Common Name(s)Rainbow Shark
Min. Tank Size50-55 gallons
Lifespan8 years
Water pH6.0-8.0
Size15cm (6 inch)
DietOmnivorous bottom feeder
Tank MatesCaution with other bottom dwellers
BreedingDifficult; spawns Oct-Nov
DiseaseSusceptible to constipation, Dropsy, and Ich

While they generally swim at a leisurely pace, Rainbow Sharks can exhibit rapid bursts of speed when necessary. Their vibrant red fins contrast beautifully against their dark bodies, making them both active and eye-catching additions to an aquarium.

They have been a favorite among aquarists for many years and continue to captivate fish enthusiasts today.

Rainbow Shark Care


Caring for them isn’t overly challenging, but specific needs must be addressed.

Factors to take into account include their temperament, sensitivity to changes in water parameters, and requirement for clean water.

As a result, it’s essential to perform routine maintenance and monitor water quality consistently. Due to these demands, there may be better options than Rainbow Sharks for novice aquarium enthusiasts.


In their natural habitat, Rainbow Sharks have a lifespan of up to 8 years. Nonetheless, in a captive environment, they usually survive for 4 to 6 years.

It is primarily through exceptional maintenance that these fishes can exceed a 4-year lifespan since they are sensitive to fluctuations in water parameters and suboptimal conditions.


Rainbow Sharks flourish in warm environments, and their preference for dwelling near the bottom in open waters indicates that they favor temperatures ranging from 23°C to 28°C (73°F to 82°F).

An aquarium heater will be essential for aquarists in many regions to maintain the optimal conditions for these fish.

Water Parameters

These sharks are sensitive to variations in water conditions, making it crucial to maintain consistent water quality. Sudden parameter changes can stress the fish and potentially increase their aggression, which may be problematic in a community tank setting.

These fish require well-oxygenated, soft water that resembles their natural habitat. Ideally, water hardness should be between 3 and 14 dKH. While a pH range of 6.0 to 8.0 is acceptable, aiming for the middle of this spectrum for optimal results is best.

Ammonia and nitrite levels must be held at 0 ppm, as levels as low as two ppm can cause stress and disease in Rainbow Sharks.

Nitrate levels should not exceed 20 ppm, and to keep their environment clean, incorporate weekly water changes of 20% to 30% as part of your routine maintenance.


Rainbow Sharks can reach a maximum length of 6 inches (15 cm) upon reaching adulthood. However, they typically measure between 1 and 2 inches (2.5 to 5 cm) when initially bought.

These fish are known for their rapid growth, particularly during their first year. In fact, during peak growth periods, they can grow as much as an inch per month.

Tank Size

Rainbow Sharks necessitate a minimum tank size of 55 gallons, with a larger tank recommended for housing multiple fish. Due to their semi-aggressive temperament and territorial nature, providing them with ample space is essential.

As these fish predominantly dwell near the bottom of the tank, the dimensions of the tank matter. Long, wide tanks offer more room for the fish compared to tall, narrow ones.

Besides tank size and shape, it’s important to include hardscape elements such as rocks, driftwood, and caves. These features assist in establishing territories for the fish and help break the line of sight, creating the impression of a more spacious tank.


Rainbow Sharks are omnivorous bottom-dwellers that consume a diverse range of food, which helps maintain their vivid and pigmented coloration. Being benthopelagic, they prefer sinking food such as sinking pellets and algae wafers, although they’ll often eat floating food.

These fish usually feed on algae, spirulina, zooplankton, and phytoplankton. Though they are sometimes sold as “algae-eaters,” they consume fewer algae than other species like Plecos, Amano Shrimp, and catfish. While they will eat algae, it alone cannot sustain them.

They can be provided with blanched vegetables like carrots, celery, peas, spinach, and zucchini, as well as raw greens such as lettuce, beet tops, and Swiss chard.

Protein-rich small crustaceans and insects, including brine shrimp, artemias, bloodworms, mosquito larvae, daphnias, and other invertebrates, are also suitable.

Since they’re not fussy eaters, feeding them should be straightforward. However, be mindful not to overfeed them.

Tank Setup & Requirements

Rainbow Sharks necessitate a tank configuration that provides ample space, and as active and swift swimmers, these fish require a tank with a generous length. A rectangular-shaped standard tank is more suitable than a tall one.

The aquarium filter for a Rainbow Shark tank should possess a sufficient flow rate to mimic the rapid rivers native to these fish.

A flow rate of at least six times the tank’s volume is ideal. For instance, a flow rate of six times the volume of a 55-gallon tank would amount to around 330 GPH (gallons per hour). This flow rate would supply the high-oxygen environment that Rainbow Sharks require.

An efficient and dependable filtration system, such as a hang-on-back filter (HOB) or canister filter, would be perfect.

Concerning the aquarium substrate, sandy substrate or polished gravel is advised, and as bottom-dwelling fish that swim quickly, sharp substrates or objects might harm them.

In terms of tank hardscape, an abundance of aquarium driftwood, caves, and rocks should be incorporated. Aquarium plants are also advantageous.

Nonetheless, hard-leaved plants should be chosen for better survivability, and ideal plants include Anubias, Amazon sword, Hornwort, Java fern, Lemon bacon, and Vallisneria.

Since Rainbow Sharks are territorial, the hardscape and plants in the tank will assist the fish in establishing its territory. This also helps break the line of sight for other fish, allowing them to avoid the Rainbow Shark’s aggression.

As they are nimble fish, having a lid on the aquarium is crucial to prevent any potential escape attempts.

Rainbow Sharks inhabit rivers, streams, and floodplains in their natural environment. They also migrate between these water bodies throughout the seasons.

also read: Peacock Gudgeon

Tank Mates

Rainbow Sharks exhibit territorial behavior, so choosing their tank companions is crucial. They often stay near the tank bottom and can defend specific areas, driving away other fish that venture too close.

Aquarists must exercise caution when selecting tank mates for these sharks. It’s advisable to avoid other bottom-dwellers, such as catfish, and opt for fish that inhabit the middle and top sections of the tank.

Choosing species of comparable or larger size with semi-aggressive temperaments helps, as they can withstand the Rainbow Shark’s propensity to intimidate other fish.

It’s also recommended to steer clear of fish that resemble them like the Bala Sharks & Red Tail Sharks since they will oppress one another.

When introducing fish to a tank, adding these Sharks at last is recommended to deter it from claiming the entire tank as its territory.

Suitable tank companions for Rainbow Sharks include Gouramis, Chromobotia, larger Rainbowfish, True loaches, Harlequin Rasboras, Danios, Barbs, Botia, Syncrossus, and medium-sized Cichlids.


Rainbow Sharks can exhibit aggressive tendencies, particularly when they mature. Younger specimens are generally less hostile and can typically coexist harmoniously with other fish.

This non-aggressive conduct may lead aquarists to assume they will always remain this way. However, as they develop, their aggression escalates, and these territorial creatures start to fight and nip at other fish that infringe on their domain.

If the tank lacks sufficient space, it’s advisable to house just one Rainbow Shark per tank.

Angelfish With Rainbow Shark

Rainbow Sharks and Angelfish typically don’t make suitable tank companions. Neither Rainbow Sharks nor Angelfish are known for their tranquil behavior. Both can exhibit territorial tendencies and aggression. Additionally, Angelfish possess elongated fins, which may be subject to nipping.

Rainbow Sharks With Cichlids

Rainbow Sharks and Cichlids might make suitable tank companions. Many Cichlids are sizable, resilient, and share a comparable temperament with Rainbow Sharks, potentially allowing them to coexist in the same aquarium.

Aggressive or semi-aggressive Cichlids can defend themselves against them. For instance, Firemouth Cichlid (Thorichthys meeki) can be an excellent option, as they are hardy fish of similar dimensions.

Bear in mind that the aquarium must be spacious enough to house all the fish comfortably. A sufficient hardscape should be present to offer the necessary hiding spots, and this also disrupts the line of sight, helping to minimize unwanted aggression.

Both Rainbow Sharks and Cichlids typically prefer more challenging water, with an ideal pH of around 7.5.

It’s important to note that there are numerous Cichlid species, and not all of them will be compatible with Rainbow Sharks.

Rainbow Shark With Betta Fish

Betta fish and Rainbow Sharks make unsuitable tank companions due to a variety of factors. Betta fish are considerably smaller, leaving them susceptible to the these shark’s aggressive behavior.

Additionally, Betta fish have a slower swimming speed compared to them. And in the event of a pursuit, the Betta fish couldn’t escape from the more enormous and belligerent Rainbow Shark.

Goldfish With Rainbow Shark

Rainbow Sharks and Goldfish typically do not make suitable tank companions due to several factors.

Firstly, these fish display aggressive behavior and are likely to bother the Goldfish. Goldfish with extended fins, like Fancy Goldfish, would be particularly susceptible to the Rainbow Shark’s assaults.

Additionally, this fish and the Goldfish have distinct preferences for water temperatures. Rainbow Sharks favor a water temperature range of 74-80°F, whereas Goldfish prefer a range of 68-74°F. Although they both belong to the Cyprinidae family, their requirements differ.

Rainbow Shark With Neon Tetras

Neon Tetra and Rainbow Shark compatibility as tank companions are uncertain. While Neon Tetras may not be particularly robust, they are swift swimmers. Furthermore, a sizable group of Neon Tetras in an ample tank may have a chance of coexisting with these fish. The aggression of the these Sharks would be distributed among the fish group. However, it is worth noting that Neon Tetras are:

  • Small fish.
  • Reaching just 1.5 inches in size.
  • Making them susceptible even if they possess quick swimming abilities.

Instead of Neon Tetras, larger Tetra species might be better suited to share a tank with Rainbow Sharks. For instance, Black Skirt Tetras and Congo Tetras would be more appropriate choices.


Reproducing Rainbow Sharks in captivity is deemed challenging, particularly for amateur fish keepers.

Most attempts to breed these fish will likely result in conflict rather than successful mating, as they are aggressive creatures with territorial tendencies. However, if they choose to mate, they will initiate by rubbing against each other.

Subsequently, the female lays her eggs on the sandy substrate, followed by the male fertilizing them by releasing his milt. The eggs are transparent and complex, requiring at least a week to hatch.

After hatching, the fry will consume their yolk sac for several days, and as parents may consume their own offspring, providing a separate tank for the fry’s growth is recommended.

The majority of Rainbow Sharks are produced in commercial farms in Southeast Asia. Even in these facilities, hormone injections might be necessary to guarantee successful spawning, and once bred, the young fish are distributed to the aquarium trade.

Distinguishing between male and female Rainbow Sharks can be difficult when they are young. However, as they mature, identifying their gender becomes more manageable.

When they reach around 4 inches in size, they can be bred. Males exhibit more vivid pigmentation and are typically slimmer, especially during mating season (October to November). Additionally, males display black streaks along their tail fins.


Should the tank conditions be inadequate, Rainbow Sharks may encounter health problems that can become fatal. Typical diseases and health concerns to watch for include constipation, swelling, Dropsy, and Ich (Ichthyophthirius multifiliis). Early treatment may help the fish recover from these issues.

In their natural habitat, Rainbow Sharks are susceptible to Betanodavirus, a pathogen responsible for viral nervous necrosis. Unfortunately, no treatment exists for this pathogen.

Antibiotics like Prazipro are considered safe to use; however, medications containing copper, salt, or dyes should be avoided.

Quarantining sick Rainbow Sharks in a separate tank during treatment is advised.

This prevents the spread of infection and safeguards other fish during the healing process, and distressed Rainbow Sharks tend to exhibit increased aggression.

Rainbow Shark Price?

As Rainbow Sharks are well-liked aquarium inhabitants, they can be found in numerous local fish stores and online shops.

They typically cost around $9 or less.

Their price is quite reasonable since they serve as a focal point in the aquarium. Moreover, most tanks can only accommodate one Rainbow Shark, so there’s no need to buy a group of them.

Nevertheless, ensure that you have the appropriate tank setup and size to house this fish before purchasing.


Having gained more insight into Rainbow Sharks and their care requirements, it’s up to you to determine if you’re willing to take on the challenge.

As discussed earlier, these fish necessitate particular conditions to flourish and coexist with other aquatic species. While they don’t demand the most extensive maintenance, they are certainly more complex to care for than a goldfish!

Despite the additional effort, Rainbow Sharks are among the most gratifying fish to maintain. Their stunning appearance, entertaining behavior, and capacity to elevate your fishkeeping experience make them worth the investment.

Fishkeeping Expert
Fishkeeping Expert
With years of collective fishkeeping knowledge, we are pleased to share the tank maintenance tips and fish care advice we've picked up along the way. Fishkeeping Expert is home to all fishkeeping tutorials and guides that will help you keep your fish healthy.


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