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


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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 feeder
Lifespan8 years
Water pH6.0-8.0
Tank MatesStock other bottom dwellers with caution
BreedingBreeding pair spawns around October to November, but they are considered difficult to breed.
DiseaseMay be susceptible to constipation, Dropsy, and Ich.

Rainbow Shark (Epalzeorhynchos frenatum) is a popular aquarium fish that has a shark-like appearance. While they aren’t true sharks, their triangular dorsal fin and body shape resembles a shark.

Rainbow Sharks are actinopterygiian, also known as “ray-finned fish.” Surprisingly, Rainbow Sharks are closely related to goldfish and carps. In constraint, true sharks belong to the Chondrichthyes lineage, also known as “cartilagenous fishes.”

Unfortunately, their wild population is currently dwindling because of habitat destruction and fishing. They are native to the warm Indochinese rivers of Mekong, Chao Phraya, Xe Bangfai and Maeklong.

They usually swim slow, but they are able to swim in very fast bursts as well if they need to. Their brightly colored red fins stand out against their black body. This is an active fish that is also beautiful, easily making it a centerpiece fish in an aquarium.

Rainbow Sharks have remained a popular aquarium fish for decades and continue to dazzle many fish keepers to this day.

Rainbow Shark (Epalzeorhynchos frenatum)
Rainbow Shark (Epalzeorhynchos frenatum)

Rainbow Shark Care 

Rainbow Sharks aren’t difficult to care for, but there are certain requirements that must be met. Some things to consider are, its temperament, sensitivity fluctuations in water parameters, and need of clean water. Therefore, regular maintenance and testing water quality is important. Due to these requirements, they aren’t the most beginner-friendly fish in the aquarium hobby.

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). An aquarium heater will be necessary for fish keepers in most climates.

Rainbow Shark Water Parameters

Rainbow Sharks are sensitive to changes in water parameters. Therefore, it is important to ensure that the water quality remains stable. If there is a sudden fluctuation in the water parameter, this can stress out the fish. This can even make them more aggressive. This can become a serious problem if they are in a community tank.

Rainbow Sharks need well-oxygenated water that is soft, which mimics their native habitat. In addition, a water hardness level of 3 to 14 dKH is ideal. As a general rule, a pH between 6.0 to 8.0 is acceptable. However, one should aim for the middle of this range for best results. 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 must remain clean, so weekly water changes of 20% to 30% should be a part of the maintenance.

Rainbow Shark Size

Rainbow Sharks can grow up to a maximum size of 6 inches (15 cm) when they reach maturity. However, the average purchase size is typically 1 to 2 inches (2.5 to 5cm).

Rainbow Sharks can grow fast especially in the first year. In fact, during its peak, it can grow up to an inch per month.

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 a 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 (Epalzeorhynchos frenatum)
Rainbow Shark (Epalzeorhynchos frenatum)

Rainbow Shark Food & Diet

Rainbow Sharks are omnivorous bottom feeders that eat a variety of food. This helps keep their striking colouration bright and pigmented. Since they are benthopelagic fish, they prefer food that sink. Sinking pellets and algae wafers are great choices. However, many of them will eat floating food as well.

Rainbow Shark will also graze on algae, spirulina, periphyton, phytoplankton, and zooplankton. They are often sold as “algae-eaters,” despite the fact that they consume less algae compared to other fish such as Plecos, Amano Shrimp, and catfish. They will graze on algae, but they will not survive on algae alone.

Other foods that can be fed include blanched vegetables such as celery, carrots, zucchini, peas, and spinach. They can also eat raw vegetables such as lettuce, beet tops, and swiss chard. Small crustaceans and insect are an excellent source of protein. This includes brine shrimp, blood worms, mosquito larvae, tubifex worms, daphnias, artemias, and other invertebrates.

Since they aren’t picky eaters, feeding them shouldn’t be an issue. However, it is important to be cautious of overfeeding.

Rainbow Shark Lifespan

In the wild, Rainbow Sharks can live up to 8 years. However in captivity, they 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 intolerant of any spikes in water parameters and poor conditions.

Rainbow Shark Tank Mates

Rainbow Sharks are territorial fish, so tank mates should be selected with careful consideration. They spend a lot of time near the bottom of the tank. They may claim certain spots for themselves, chasing away any fish that comes too close to it.

Fishkeepers need to be very careful when picking tank mates for Rainbow Sharks. Other bottom-dwelling species such as catfish should be avoided. Instead, choose fish that occupy the middle and upper levels of the tank. Species of similar or larger size, that have a semi-aggressive temperament would be able to tolerate the Rainbow Shark’s habits of intimidating other fish. It is also best to avoid fish that look similar to Rainbow Sharks (e.g. Red Tail Sharks and Bala Sharks) as they will harass each other.

When adding fish into a tank, it is best to place the Rainbow Shark in the tank last, which will help prevent the fish from trying to claim the entire tank as its own.

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

Are Rainbow Sharks Aggressive?

Rainbow Shark can be aggressive fish, especially as fully grown adults. Juvenile specimen are less aggressive, and they usually can coexist with other fish peacefully. This peaceful behavior may mislead fishkeepers into thinking they will remain this way forever. However, aggression increases as the Rainbow Shark grows, and this territory-obsessed fish will begin brawling and biting at other fish that challenges their territory. If there isn’t enough space in the tank, it is best to keep a single Rainbow Shark per tank.

Rainbow Shark Care Guide – My Favorite Community Fish

Angelfish and Rainbow Shark

Rainbow Shark and Angelfish is generally incompatible as tank mates. Both Rainbow Shark and Angelfish aren’t exactly peaceful fish. They can both be aggressive and territorial. Angelfish have long fins, which might be nipped.

Cichlids and Rainbow Shark

Rainbow Shark and Cichlids may be compatible as tank mates. Since many Cichlids are large, tough, and have a similar temperament to Rainbow Shark, they may be able to coexist in the same tank. Aggressive or semi-aggressive Cichlids will be able to defend themselves against Rainbow Sharks. For example, Firemouth Cichlid (Thorichthys meeki) can be a great choice since they are tough fish that are similar in size.

Keep in mind that the tank must be large enough to accommodate all fish in the tank. There should be enough hardscape to provide the necessary hiding places. It also breaks the line of sight, which also helps reduce unnecessary aggression. Both Rainbow Shark and Cichlids generally prefer hard water, and a pH of around 7.5 is ideal.

There are many species of Cichlids, and not all species will be compatible with Rainbow Sharks.

Betta fish and Rainbow Shark

Betta fish and Rainbow Sharks are incompatible as tank mates for several reasons. Betta fish are far too small, making it vulnerable to the Rainbow Shark’s attacks. Betta fish also swim slower compared to Rainbow Sharks. If there is a chase, the Betta fish will not stand a chance against the larger and aggressive Rainbow Shark.

Goldfish and Rainbow Shark

Rainbow Sharks and Goldfish are generally not compatible as tank mates for a few reasons.

First, Rainbow Sharks are aggressive and they will most likely harass the Goldfish. Goldfish with long fins such as Fancy Goldfish would be exceptionally vulnerable to the attacks of the Rainbow Shark.

Next, Rainbow Shark and Goldfish have different requirements regarding their water temperatures. Rainbow Shark prefer a water temperature of 75-80°F. On the other hand, Goldfish prefer a water temperature of 68-74°F. Even though they belong to the same family (Cyprinidae), they have different requirements.

Guppies and Rainbow Shark

Guppies and Rainbow Shark are generally not compatible as tank mates. Since Guppies only grow to approximately 2 inches (5.1 cm), they would be vulnerable to attacks from the Rainbow Shark. Many types of Guppies have long fins, making them slow swimmers as well. These Guppies would be especially vulnerable to the attacks from the Rainbow Shark.

Neon Tetras and Rainbow Shark

Neon Tetra and Rainbow Shark may or may not be compatible as tank mates. Neon Tetras aren’t tough, but they are fast swimmers. In addition, a large group of Neon Tetras in a large tank may be able to coexist with Rainbow Sharks. The Rainbow Shark’s aggression would be spread out among the group of fish. With that said, Neon Tetras are small fish, reaching only 1.5 inches in size. This makes them vulnerable, even if they are able to swim quickly.

Instead of Neon Tetras, larger species of Tetras would be more compatible with Rainbow Sharks. For example, Black Skirt Tetras and Congo Tetras would be more ideal.

Rainbow Shark Tank Setup

Rainbow Sharks need a tank setup that consists of adequate space. They are active fish that are able to swim fast, so a tank with plenty of length is important. Rather than a tall tank, a standard tank fish a rectangular shape would be more effective.

The aquarium filter for a Rainbow Shark tank should have enough flow rate to imitate the fast flowing rivers that they are native to. A flow rate of at least six times the volume of the tank is ideal. For example, a flow rate of six times the volume of a 55 gallon tank would be approximately 330 GPH (gallons per hour). The flow rate would provide the high-oxygen environment that Rainbow Sharks need. A capable and reliable filtration system, such as a hang-on-back filter (HOB) or canister filter would be ideal.

Regarding the aquarium substrate, sandy substrate or smooth gravel is recommended. They are bottom dwellers, and they swim fast. Sharp substrate or objects may injure the fish.

Regarding the hardscape of the tank, plenty of aquarium driftwood, caves, and rocks should be used. Aquarium plants are beneficial as well. However, plants with hard leaves should be selected if you expect it to survive. Plants such as Anubias, Amazon sword, Hornwort, Java fern, Lemon bacon, and Vallisneria would be ideal. Since Rainbow Shark are territorial, the hardscape and plants in the tank will help the fish carve out a territory for itself. It can break the line of sight with the other fish as well. This would help the other fish evade the aggression of the Rainbow Shark. Since they are agile fish, it is important to keep a lid on the aquarium, in case they decide to jump out of the water.

In their native habitat, Rainbow Shark are known to live in rivers, streams, and flood plains. They would migrate in between these bodies of water throughout the season as well.

Rainbow Shark Breeding

Breeding Rainbow Sharks in captivity is considered to be difficult, especially for a hobby aquarists. Most efforts to breed the fish will most likely result in a fight instead. They are aggressive fish with territorial instincts. However, if they do decide to mate, they will start to against each other. Afterwards, the female will deposit the eggs on the sandy substrate. Soon after, the male will fertilize the eggs by releasing his milt. The eggs are clear and hard, and they need at least a week to hatch. After they hatch, the fry will absorb their yolk sac for a few days. Since the parents may eat their own fry, providing a separate grow-out tank for the fry would be ideal.

The majority of Rainbow Sharks are bred in commercial farms in Southeast Asia. Even in these commercial farms, hormone injections may be required to ensure successful spawning. After they are bred in the farms, the juveniles are distributed to the aquarium trade.

It is difficult to distinguish the difference between a male or female Rainbow Shark when they are young. Once they mature, it becomes easier to tell the difference. Once they reach approximately 4 inches in size, they can be sexed. The males display more vibrant pigmentation. The males are typically more slender, especially during breeding season (October to November). The males also possess black streaks along their tail fins.

Rainbow Shark Disease

If conditions in the tank are unsuitable, Rainbow Sharks may develop health issues that can be life-threatening. Common diseases and health issues to be aware of include constipation, bloat, Dropsy, and Ich (Ichthyophthirius multifiliis). The fish may recover from the health issues if they are treated early.

In the wild, Rainbow Sharks are known to be vulnerable to Betanodavirus, a pathogen which causes viral nervous necrosis. There is no available treatment for this pathogen.

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 during treatment. This will not only prevent the spread of infection, but it will keep other fish safe during the recovery. Rainbow Sharks in distress are often more aggressive than usual.

Where Can I Find Rainbow Shark for Sale?

Since Rainbow Shark are popular aquarium fish, they are available in many local fish stores and online stores. They are usually available for approximately $9 USD or less. Considering that they are a centerpiece fish, they aren’t too expensive. In addition, most tanks would only be able to house one Rainbow Shark, so you wouldn’t be purchasing a school of these fish. However, make sure you have the right tank setup and tank size to accommodate this fish before purchasing.

Rainbow Shark vs Albino Rainbow Shark

Albino Rainbow Sharks (Epalzeorhynchos frenatum) and Rainbow Shark (Epalzeorhynchos frenatum) are very similar. That is because Albino Rainbow Shark is a variety of Rainbow Shark. They have the same red fins, but they have a white body. Its temperament and biology is identical to its more pigmented counterpart. The only difference between the two is the colouration.

Rainbow Shark vs Bala Shark

Rainbow Sharks (Epalzeorhynchos frenatum) and Bala Sharks (Balantiocheilos melanopterus) come from the same family of Cyprinidae, but they are quite different. Bala Sharks are timid fish that do best in schools. In comparison, Rainbow Sharks do better alone. Bala Sharks are also known as Tricolor Shark, Tricolor Sharkminnow, Silver Bala, Silver Shark, and Shark Minnow. For a Bala Shark, any sudden movement may trigger the fish to dart about anxiously, even jumping out of the tank if there is no lid on the tank. Bala Sharks are bigger in size, compared to Rainbow Sharks. Bala Sharks grow to approximately 8 inches (20 cm) in size. They have a silver body with black markings on their dorsal, caudal, anal, and pelvic fins. Bala Sharks have a peaceful temperament and make great community fish. However, they may be bullied by more aggressive species, such as Rainbow Sharks.

Rainbow Shark vs Red Tail Shark

Rainbow Shark (Epalzeorhynchos frenatum) and Red Tail Sharks (Epalzeorhynchos bicolor) look very similar in appearance. They are often mistaken for one another. However, it is very easy to distinguish the two species since Red Tail Sharks have the red coloration only on their tails. In contrast, Rainbow Sharks have the red coloration on all of their fins. Red Tail Sharks are also known as Red-Tailed Black Shark, Red Tail Labeo, Fire Tail Shark, and Red Tail Shark Minnow. They are native to Thailand and their wild population is currently endangered. However, they remain popular among fishkeepers due to their striking appearance. Red Tail Sharks and Rainbow Shark are similar in size and temperament. Since they are both territorial and aggressive fish, keeping the two fish in the same tank is generally not recommended.

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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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