Fast, robust fish that live in the top and middle of the tank can live with a rainbow shark. Choose tank mates that are peaceful but quick and sturdy enough to avoid a territorial bottom dweller. Rainbow sharks reach about 6 inches, so the tank also matters: use at least 55 gallons, and a long tank of 4 feet or more is better.
Rainbow sharks get more territorial as they age, and they are hardest on fish that look like them or that live on the bottom. These fish are usually safe choices:
- Zebra danios
- Dwarf neon rainbowfish
- Congo tetras
- Neon tetras
- Rummy nose tetras
- Honey gourami
- Rasboras
- Angelfish
- Boseman’s rainbowfish
- Caridina shrimp
- Ghost shrimp
- Nerite snails
- Mystery snails
Shrimp are the riskiest items on this list. Rainbow sharks are omnivores, and small shrimp can end up as food, especially Caridina shrimp. Give them dense plants and caves if you try it. Snails are usually safer. Angelfish are slow, so the shark may harass them. Only try them in a large tank with plenty of space and hiding places, and be ready to separate them. Small neon tetras are quick enough in most cases, but keep them in a group of 6 or more.
What Fish Should You Avoid With a Rainbow Shark?
Avoid keeping a rainbow shark with other rainbow sharks or other freshwater sharks. These fish are highly territorial and will fight and injure each other. Seriously Fish says that rainbow sharks are especially aggressive toward similar-looking species, and notes that red-tailed sharks, other Epalzeorhynchos species, and algae eaters of similar shape are attacked constantly.
Don’t keep a rainbow shark with other bottom dwellers like most catfish and plecos. Seriously Fish advises against other bottom-dwelling fish and cichlids. Loaches are a partial exception, since Seriously Fish lists several loach genera as tolerated by rainbow sharks, but go carefully and be ready to separate them.
What Should You Watch For?
- Tank size: a small tank makes aggression worse. Use 55 gallons as the minimum, and more if you want mixed tank mates.
- Hiding places: caves, wood, and plants let other fish break the line of sight.
- Chasing that does not stop: if the shark keeps bullying one fish, remove the target or rearrange the decor to reset territories.
- Age: a juvenile shark can be mild and then become a bully as it matures, so recheck the tank as it grows.