Are Rainbow Sharks Aggressive?

Are Rainbow Sharks aggressive? Whilst rainbow sharks are not really aggressive by nature, they can be very territorial. If they don’t have enough space or if they feel like they or their territory is being threatened they will defend it and that is when you can expect to see signs of aggression! 

Like with any tropical fish if you give them the right conditions, Rainbow Sharks will thrive, but I would suggest that beginners avoid them – they are better suited for more experienced fishkeepers.

Rainbow Sharks - An Overview

Rainbow sharks (  Epalzeorhynchos frenatus ) also known as Ruby sharks or Red-Finned sharks and can grow up to around 6 inches long when fully grown although some rainbow sharks have been recorded as large as 10 inches long. Rainbow sharks live on freshwater bottoms in the river basins of north eastern India and Nepal, in Indonesia (Kalimantan) and Cambodia (Tbeng Meanchey). They inhabit sandbanks at depths between 1 – 5 meters where there is plenty of shelter and plenty of food.

Rainbow sharks are very common fish in the aquarium trade where rainbow shark prices vary from $12 – 90 depending on the size of rainbow shark you wish to buy. Some rainbow sharks have been recorded at over 7 years old in captivity, whilst rainbow sharks in the wild only live up to about 4 years old. The rainbow shark has a normal lifespan of between 4-6 years if properly cared for in an aquarium.

In their natural habitat rainbow sharks don’t have a wide range of predators and are generally passive and non-aggressive but will compete over territory or food. It’s important to understand rainbow shark aggression before making your decision to buy rainbow sharks for your aquarium

As we’ve already mentioned above, rainbow sharks can be very territorial and this means it is usually wise to only house one rainbow shark in a tank. Being confined in a small tank will increase the likelihood of a rainbow shark being aggressive. You’ll therefore need an aquarium of at least 30 gallons (a bigger tank of around 50 gallons is better) and a longer tank is more preferable than a taller one

Rainbow sharks are bottom dwellers and are most happy in tanks with plenty of hiding places, such as rocks and caves where they feel safe from predators. They may often swim along the bottom of their tank or live among the substrate, meaning rainbow sharks don’t usually come into contact with other fish unless that is what they want.

Your rainbow shark may become territorial and therefore aggressive towards other fish in your aquarium that bear a resemblance to rainbow sharks. If you’re housing rainbow sharks with these species, then try introducing them at the same time so that rainbow shark aggression is minimised.

Are Rainbow Sharks Fin Nippers?

Rainbow sharks may well nip the fins of other fish in their tank! As rainbow sharks don’t have many predators in the wild, they’ve learned to survive by mastering attacks from behind and below. Fin nipping is an instinctive behaviour that allows them to defend themselves against threats.

Rainbow sharks are also less likely to nip the fins of fish that have a different body pattern as rainbow sharks, or those with long and flowing fins – this includes bettas.

Do Rainbow Sharks Bite?

When threatened or if they are fighting over their territory rainbow sharks won’t hesitate to bite. You should therefore be mindful of rainbow shark habitat and rainbow shark tank mates, especially if you keep rainbow sharks with small or vulnerable fish in your aquarium.

Rainbow sharks may also bite dead or dying fish so it’s important that you remove any corpses from their tank immediately to avoid illness.

Keeping rainbow sharks in an overcrowded tank is another reason why rainbow sharks are likely to bite – they become aggressive when stressed by the excess amount of activity going on around them.  A 30 gallon tank is the bare minimum for rainbow sharks as it provides rainbow sharks with enough space so that they don’t feel threatened or have to compete for territory and food but you would have to be very careful with what else you add to the tank – the more space the better as far as rainbow sharks are concerned.

Rainbow Shark Suitability For Your Aquarium

As rainbow sharks like to live on the substrate you will need to ensure that there is a good amount of substrate in your aquarium, ideally one that will stay clean as rainbow sharks like to sift through the sand. Sand is also favourable for rainbow shark habitat because it mimics their natural environment a lot better than may other substrates.  It’s also important that you change the substrate regularly as rainbow sharks are likely to use it as part of their toilet routine.

Larger tanks work best with rainbow sharks – more space means less nipping and less stress for rainbow sharks! A minimum tank size of 30 gallons is recommended but bigger aquariums allow rainbow sharks to be calmer and therefore less prone to aggression. Another aspect which can cause rainbow sharks to become aggressive is over-crowding – rainbow sharks often nip other fish in the tank or may bully them if they feel crowded. Always be mindful of this when adding rainbow sharks to your aquarium, especially if you’re planning on housing rainbow sharks with small fish.

What Can Live With A Rainbow Shark?

Fish that tend to stay in the top half of the tank make the best tank mates for rainbow sharks. The below list several possible tank mates:

  • Barbs, especially tiger barbs
  • Angelfish (wild rainbow sharks inhabit the same waters as rainbow fish)
  • Bettas (rainbow sharks will shouldn’t nip bettas unless they feel they are invading their territory – as stated already make sure they have enough space!)
  • Gouramis
  • Rasboras
  • Rainbow fish
  • Zebra Danios
  • Congo Tetras
  • Nerite Snails (Your rainbow shark will have no interest in a Nerite Snail and vice versa)
  • Ghost shrimps (These creature can be great fun to watch. They can become near transparent and so they don’t induce aggressive behavior from a rainbow shark)
Harlequin Rasboras can make good tank mates for a Rainbow Shark

How Many Rainbow Sharks Can Be Kept In A Tank?

It is generally advisable to only keep one rainbow shark in a tank because they are so territorial. If you do want to have more than one rainbow shark I would advise keeping no fewer than five as this limits the amount of aggression one fish would face from the dominant shark as there would be others for it to chase!


Why Are My Rainbow Sharks Fighting?

If rainbow sharks are in an aquarium that is too small or have been introduced to the tank with incompatible tank mates, rainbow sharks can become aggressive. Rainbow sharks may also fight over territory, food and oxygen. Try adding more rainbow shark habitat (rocks and plants) or moving rainbow sharks into a larger tank – at least 30 gallons  is recommended so they feel less threatened and aren’t forced to compete for territory or food.

Rainbow Sharks shouldn’t be kept in tanks smaller than 30 gallons as small tanks don’t provide rainbow sharks with enough space to swim around freely and prevent them from getting aggressive. It’s important to watch out for aggressive fish during rainbow shark selection as most species of rainbow shark are highly territorial and will fight fish with similar body shapes (or rainbow shark species) as themselves.

Which Is More Aggressive Rainbow Shark Or Red Tail Shark?

It is difficult to compare rainbow sharks and red tail sharks as rainbow sharks are so variable in their behavior. Rainbow shark aggression depends on numerous factors such as the size of the rainbow shark, its age, the number of rainbow fish in the tank at one time and how many fish there are with similar body shapes to it. Red tail sharks are more aggressive than rainbow sharks because red tails don’t like smaller fish swimming too close to them. In a small space rainbow shark may feel territorial and nip other rainbow fish but rarely will rainbow sharks bite each other repeatedly or for long periods of time.

Should I Put A Molly With My Rainbow Shark?

Mollies are generally considered suitable rainbow fish tank mates but it is best to introduce a Molly into your rainbow shark’s tank at the same time, rather than before or after them.

Mollies are generally considered suitable rainbow fish tank mates

What Is The Minimum Tank Size For Rainbow Sharks?

The absolute bare minimum tank size for keeping one rainbow sharks is 30 gallons but really, a tank of 50 gallons or more is better. A tank that is 36 inches long, with a depth of 19 inches and a width of 18 inches would be ideal for a rainbow shark.

Is My Rainbow Shark Male Or Female? (How can I tell?)

There are a few clues to look for when trying to determine whether a rainbow shark is male or female:

  • Males tend to have thinner bodies than females
  • The body of a male is usually brighter
  • Males have black lines on their tailfins whilst the females don’t (however younger males may not have the black lines as they tend to come when the fish gets older)

Are Rainbow Sharks Aggressive? - Conclusion

Rainbow sharks do have a tendency to be aggressive if they are kept in too small of an aquarium or with rainbow shark tank mates that are considered incompatible. If you select their tank mates wisely and provide them with enough space, food, caves, rocks and plants, rainbow sharks are generally pretty calm and peaceful fish.

The rainbow shark is a beautiful fish that can provide years of joy to a fairly experienced fishkeeper.