Rainbow Shark: Species Profile

Category: Freshwater Shark

Common Names: Rainbow Shark, Red-finned Shark

Scientific Name: Epalzeorhynchos frenatus

Family: Cyprinidae

Minimum Tank Size: 55 Gallons

Care Level: Moderate

Temperament: Semi-Aggressive

Max Size: 6 Inches

Temperature: 72-80 F

pH: 6.5-7.5

Tank Level: Bottom

Colors: Black, Red, Silver

Diet: Omnivore

Breeding: Difficult

Rainbow Shark against Plants

Rainbow Shark Overview

Rainbow sharks, a freshwater fish, are not as common as other pet types. They typically require lots of space and are not a low-maintenance species compared to alternatives. Given that, they are not an ideal option for beginners.

Distinguishing Features of the Rainbow Shark

You can easily pick a rainbow shark out of a school of fish by looking at its bright red or orange fins that contrast beautifully against their black or gray bodies. Some rainbow sharks even have a dark blue body, though it’s not as expected.

As the name suggests, rainbow sharks resemble a shark’s body, though it’s not a true shark. Its dorsal fins have roughly 11 branching rays and a tailfin that comes in at a fork.

Rainbow sharks have flat faces with rounded noses and an eye on each side of their head. These slender fish start with a rounded shape near their head and then tapers off towards the tail.

The only known additional type of rainbow shark is the albino, which is very rare. While the standard rainbow shark has either a black, gray, or blue body, albino varieties have a light-colored white, pink, or yellow body.

Luckily for lovers of the rainbow shark, this species is relatively inexpensive, usually under $5, and many pet stores have them. You may even spot an albino rainbow shark while you’re there.

The only downside to owning a rainbow shark is that you’ll have to get a tank just for them or prepare to pair them with other fish (so long as they aren’t other bottom feeders).

These algae-eating and active swimming fish are highly entertaining but require more care than other freshwater fish. Though not impossible for beginners, you need to meet all of their needs to ensure a happy life for a rainbow shark.

Rainbow Shark with Plants Behind

Origin of the Rainbow Shark

Rainbow sharks are freshwater fish species native to rivers in Southeast Asia, including Xe Bangfai, Mekong, Chao Phraya, and Maeklong.

Unfortunately, Xe Bangai has dams that restrict rainbow sharks’ migration patterns, causing a drop in their species in the wild.

You can easily find rainbow sharks near the river bottom. Living in sandy substrates, they feed on algae and plankton.

Rainbow sharks will migrate into more flooded areas and then return to the river once the flood dries up when the seasons change.

Average Rainbow Shark Sizes

Rainbow sharks may grow six to eight inches in length when living in their natural habitat. If they get good care in captivity, they will grow roughly four two six inches.

Male and female rainbow sharks don’t vary in length, though females will have a wider midsection.

Lifespan of the Rainbow Shark

Rainbow sharks have a lifespan of about eight years in the wild. If they get proper care and have an appropriate environment, rainbow sharks typically live up to six years in a tank.

Male vs Female Rainbow Sharks

The primary way to differentiate a male from a female rainbow shark is with their colors. Males have brighter fins compared to females, who have duller colors.

Males also have small gray lines while females do not. The males often have black lines on their rear fins once they mature.

As previously mentioned, female rainbow sharks have thicker mid-sections, and males appear to be more slender.

It can be hard to tell the difference between male and female sharks until they reach maturity.

Temperament of Rainbow Sharks

Rainbow sharks tend to stay by themselves in the wild and don’t bother other fish. If a fish does come into its territory, it will assert dominance. Wild rainbow sharks will create individual domains.

So, if you place another fish in the same tank as a rainbow shark, you may notice aggression. That is most prevalent in reduced environments.

As young fish, rainbow sharks spend most of their time hiding. As they mature, they become more dominant and may even bite, chase, or headbutt any other bottom-dwelling fish.

Since younger fish are so timid, adding another rainbow shark or other fish to the aquarium can be tempting. However, as they age and their territorial nature increases, this could create issues later.

Albino Rainbow Shark

Rainbow Shark Tank Parameters

Even though rainbow sharks are freshwater fish, their environment needs to be the right size, temperature, and pH, and they must have plenty of room to hide and swim.

Minimum Tank Size

For one rainbow shark, the tank will need to be at least 50 gallons with a length of around four feet. They require plenty of horizontal swimming space, especially with other fish, or they can be territorial.

If you plan to add another rainbow shark, you’ll need a 100-gallon tank to ensure they have plenty of room to swim without becoming aggressive with each other.

Keep in mind that the tank will have more than just water; you will need to add plenty of plants, rocks, caves, and other fish decors to allow them to hide.

The more space a rainbow shark has, the less likely they will become aggressive.

Water Parameters

Because rainbow sharks are native to warm, fast-flowing freshwater rivers, they need a tank that mimics this environment as best as possible.

Even though rainbow sharks can thrive in waters in temperatures between 72-82 degrees Fahrenheit and 6.5.-7.5 pH, extreme jumps can cause stress and aggression.

The best way to avoid rapid temperature changes is to purchase a high-quality heater that can maintain a steady temperature.


The ideal temperature for a rainbow shark is 77 degrees Fahrenheit, though between 72-82 degrees Fahrenheit works as long as it’s stable.


The pH should be between 6.5 and 7.5, and like the temperature, it shouldn’t fluctuate.


You should use only freshwater (0 ppt). Rainbow sharks must be in high-quality water at all times, so be sure to keep an eye on ammonia, nitrites, and nitrates.

Tank Setup

Because rainbow sharks are native to fast-moving streams, they have to have a filter to replicate this fast water flow.

In addition, you can do the following to increase water flow:

  • Add air stones to their tank
  • Strategically place objects so that they don’t weaken the water flow
  • Use powerheads or wavemakers

Even though rainbow sharks spend most of their time on the bottom of the tank, they may try to jump out. Ensure a sturdy lid on the aquarium to prevent them from flying out. Once they’re used to their new home, you may be able to remove the cover.


Like their native environment, rainbow sharks prefer sandy substrate in captivity. Sand is an excellent option because it mimics their natural habitat and is easy to clean.

You can also use gravel, but it should only be small pieces. Large chunks of rock risk scratching your bottom-dwelling fish, which could lead to infection. Additionally, gravel tends to collect waste and is more challenging to clean than sand.

However, plenty of people have rainbow sharks that thrive with a gravel bottom, but it does need regular cleaning to maintain hygiene.

rainbow shark


Rainbow sharks love a decorated home because it gives them plenty of hiding spots. They have plenty of places to stay out of sight in their natural habitats, so do your best to imitate that design.

Caves are a favorite hiding and sleeping spot for rainbow sharks, so add at least one to their tank. You can also add hollowed decor, driftwood, rock formations, or even fun decorations.

Above all, ensure there is variety within their new home.


As with decor, rainbow sharks enjoy having aquarium plants to hide behind and snack on.

Best plants for rainbow shark tanks include:

  • Anubias
  • Amazon sword
  • Hornwort
  • Java fern
  • Java moss
  • Lemon bacopa
  • Vallisneria.

Fake plants also make a great addition to a rainbow shark tank; be sure that they don’t have any sharp edges that could scratch your fish.


Because they’re freshwater fish, LED aquarium tank lighting is recommended, as it provides natural day and night cycles. However, they don’t need any specific lighting.


As previously mentioned, rainbow sharks are accustomed to fast-flowing stream water. Adding a filter that provides plenty of water flow will make your fish more comfortable in their environment.


Heating is essential to the health and temperament of your rainbow sharks. Not only do you need to stick within a specific range, but it needs to stay within a degree or two of the same temperature at all times.

A specialized heater that can maintain a consistent water temperature is ideal for keeping rainbow sharks healthy, comfortable, and less aggressive.


Rainbow sharks are omnivores and will eat a little bit of everything. They enjoy eating algae that will naturally form at the bottom of their aquarium. If their tank doesn’t have many algae, they’ll happily eat it in flake or tablet form.

You can also feed your rainbow sharks boiled vegetables, and the high nutrient content will allow their colors to develop.

Boiled vegetables include:

  • Chunks of zucchini
  • Peas
  • Spinach leaves
  • Romaine lettuce

Before adding any boiled veggies to the tank, make sure they cooled to room temperature.

For a balanced diet, feed rainbow sharks small pieces of meat regularly. Their top choices include:

  • Brine shrimp
  • Bloodworms
  • Artemias
  • Daphias
  • Crustaceans
  • Aquatic insects
  • Insect larvae

During feedings, keep an eye on any food they don’t eat. Quickly clean out any excess food particles to avoid rotten waste to collect.

Give your rainbow sharks a combination of meat and plant foods two to three times per day. Only give them what they can eat in five minutes to avoid overfeeding your fish.

If they don’t receive proper nutrition as young fish, they may have stunted growth and dull-colored fins.

Albino Rainbow Sharks against Black Background


Breeding rainbow sharks is challenging, and it’s unlikely that they’ll produce any offspring. Male and female rainbow sharks tend to clash and may even attempt to attack each other.

When to Breed Rainbow Sharks

Before attempting to breed your rainbow sharks, they need to be their adult length of four inches. Additionally, it’s easier to distinguish between male and female fish once they’re matured.

Setting Up the Breeding Tank

Breeding tanks for rainbow sharks look different from their standard separate tanks.

Here is what you’ll need:

  • A tank that is at least 75 gallons, ideally bigger
  • Lots of plants and decor for shelter
  • Gravel for the female to lay her eggs

How to Initiate Breeding

First, introduce a male and female rainbow shark to their new tank. Give them about a week to see if they can live peacefully together. If not, you’ll probably need to try a different pair.

If they seem to get along, give them plenty of protein-rich foods like brine shrimp or bloodworms.

Rainbow sharks exhibit mating behavior by rubbing against each other. Once they mate, the female rainbow shark will scatter the eggs along the gravel. Then, the male rainbow shark fertilizes them.

How to Care for Rainbow Shark Fry

If successful, set up a new tank for the newborns and transfer the eggs using a net. Avoid adding a filter to this tank, as it may suck the fry into it.

Expect them to hatch within a week, and they will feed off their yolk sacs. After they eat all of their sacs, give them liquid food for a couple of weeks.

You can move the newborns into their main aquariums once they’re around an inch long.

Albino Rainbow Shark

Common Diseases

With proper care, rainbow sharks tend to be hardy fish. Without proper care, they are susceptible to issues such as:

  • Bloat: Like humans, your rainbow shark’s belly will look full and bloated. This happens when they’re overfed and unable to pass fluids, gasses, and foods.
  • Constipation: Rainbow sharks need a balanced diet with plenty of fiber. Without vegetables, they can become constipated.
  • Ich: It’s essential only to add decor without sharp edges; otherwise, they can get scratched resulting in Ich or “White Spot Disease.”

Potential Tank Mates

As bottom feeders, rainbow sharks prefer to dwell on the bottom of their tank and will be territorial in their area. Avoid adding any other bottom dwellers that may threaten their territory. Instead, opt for fish that spend their time at the top or middle of the tank.

Good tankmates include:

  • Rasboras
  • Danios
  • Gouramis
  • Rainbowfish

Worst tankmates include:

  • Bala sharks
  • Redtail sharks
  • Cichlids
  • Catfish

Creating the Best Environment for Rainbow Sharks and Their Tank Mates

Even with the best tank mate, rainbow sharks may still show aggression if you place another fish in with them. They view their tank as their territory and will feel as if an invader just swam in and took over.

To avoid this, start placing other fish in the tank first and adding the rainbow shark last. Because your rainbow shark will join other fish, they will be less likely to see it as their territory.

With more tank mates, you’ll need extra plants and decor for them to hide behind. If they cannot see the fish atop the tank, they’re less likely to attack.

Fish close to the same size or bigger than rainbow sharks tend to work best. Rainbow sharks may try to assert dominance over smaller fish but typically won’t mess with fish their size.