Red Tail Sharks: Why They’re Aggressive & Calming Them Down

Keeping Red Tails in a community tank is no small venture; however, it is doable! With the correct species composition, you can keep a diversity of fish. However, what are the other factors at play? Why do Red Tail Sharks attack other fish, and how do you reduce their aggression?

Red Tail Shark | Photo 108905177 © Tomcox8 |

Red Tail Shark Aggression, Causes And Responses 

Red Tail Sharks are semi-aggressive in temperament. They are very territorial and will readily chase intruders from their area.

Consequently, when Red Tails are juveniles, they are quite “shy,” as they become adults and establish territories, their aggressive behavior beings.

Aggressive behavior from Red Tails Sharks is not as severe as some species. They generally chase intruders out of their territory with limited biting

They can, however, chase fish to the point of exhaustion, which is not ideal.

Note: It is highly recommended NOT to keep more than one Red Tail Shark per tank. Unless you plan on having a very large tank, where each fish can establish its own suitable territory, it is best to keep them individually. 

Ways To Mitigate Aggression In A Community Tank With Red Tail Sharks

Examples of the best ways to reduce and prevent aggression in your community tank are listed below.

  • A larger tank size. Although the minimum tank size is 55 gallons, it would be even better if you could have between 75 and 100 gallons.
  • Including rocks, driftwood and plants creates visual barriers so that other fish will be out of sight of Red Tail Sharks. 
  • Territorial fish will also generally use these “landmarks” to establish their territory

So by including larger objects on the tank’s floor, Red Tail Sharks will potentially choose a smaller section for their territory (especially if there is a cave structure).

  • Compatible tank mates. Some fish are generally better to keep together than others. Selecting the correct fish will help reduce stress and aggression.

Don’t Choose the Wrong Fish

When choosing tank mates for a community tank with a Red Tail, it is important to: 

  • Choose fish of a similar or less aggressive temperament
  • Choose fish that have specific adaptations/behaviors to deal with more aggressive fish
  • Choose fish that have comparable tank requirements in terms of pH, temperature, and décor. (I’ll discuss what these are later.)

It is recommended that other semi-aggressive fish be added to the community tank, alternatively, peaceful schooling fish

Faster moving fish that prefer the middle and upper reaches of the tank are also a great idea. 

These fish will avoid interacting with your Red Tail Shark and have the speed to move away quickly enough to avoid getting hurt.

Red Tail Sharks will spend the majority of their time in the bottom zone of the tank, eating algae off of rocks and plants (they do, however, venture and explore in the middle section as well). 

For this reason, it is recommended to rather not keep bottom-dwelling species like Cichlids or Plecos, as they potentially will come into the Red Tail Shark’s territory more frequently. 

Some of the Better tank mates for them include:

  • Zebra Danios
  • Congo Tetras
  • Honey Gourami

I have a larger list of the tank mates that work best for red tail sharks here:

Red Tail Shark Tank Requirements 

Although the Red Tail Shark (Epalzeorhynchos bicolor) is not the most aggressive fish in the pond, there are still some definite restrictions when keeping them in a community tank setting. 

These attractive fish originate from Thailand, in swampy and freshwater lake areas. They are part of the Carp family (Cyprinidae) and were dubbed “shark” due to their dorsal fin, which resembles a shark’s.

These fish are moderately easy to keep fish and can reach a size of between four and six inches

Although they are quite small, the minimum tank size recommended is 55 gallons. These are quite active fish, and so a larger tank allows for swimming space.

Some tank requirements include:

  • Temperature: 72-790F
  • pH: 6.8-7.5
  • Hardness: 5-15 dH
  • Tank setup:  It is recommended to have fast water flow in the tank to mimic similar conditions to their natural environments.

Other tank requirements include using gravel or larger rocks as a substrate (your Red Tails may eat smaller stones!). 

The inclusion of live plants in the tank is also recommended. However, even though Red Tails shouldn’t eat the foliage, some of the other species may.

Red Tail Sharks are known for their jumping behavior, so a lid must be on top of the tank.


Red tail sharks are a naturally aggressive fish that likes to maintain a territory at the bottom of an aquarium and chase any intruders out of the space its claimed for itself.

This issue can be exacerbated if you choose the wrong tank mates or have more than one of them in an aquarium, so it’s important to pick tank mates that stay towards the top of the aquarium or that can stand up for themselves.