The Red-tailed black shark or redtail shark is a type of carp that was originally found in Thailand. Due to excessive poaching, the redtail was thought to have become extinct in the wild, however, due to their popularity within the aquarium trade the breed continues to thrive in private collections.

Tank Requirements

  • Very Cautious Community or Specialist Tank
  • Temperatures between 22°C and 26°C
  • Water between pH 6.0 and pH 8.0
  • Lots of hiding spaces
  • Minimum of 52 gallons (200 litres) per fish
  • One fish per tank
  • Fast flowing water
  • Varied substrate sizes
  • Varied decoration & plants to allow for varied algae growth

These fish are semi-aggressive. When kept as a single fish in a community tank they get along with most other fish, they do not like fish that are the same shape as them such as Golden Algae Eaters & Silver Sharks. They should not be kept with fish like cichlids, catfish or other bottom dwellers.

When adding to a community tank, these fish are better to be added last to the tank so they are last to establish a territory to help curb aggression. You should also ensure your aquascape breaks up the vision of the tank, reducing the size of the territory these fish can claim.


  • These are omnivores
  • They will graze on algae that grows on rocks, plants, and glass
  • They enjoy a mixed diet of bloodworm, daphnia, brine shrimp, flaked food, pellets

In my experience, these fish are not fussy eaters. They will eat pretty much anything that is put in the tank. They particularly enjoy meaty foods such as bloodworm, but they also like a bit of cucumber. Feeding wise, you couldn’t ask for an easier fish.

They also enjoy grazing on algae that has built up in the tank.

Male & Female Redtail Shark

Red Tailed Shark
Red Tailed Shark

Size: Maximum length 13cm

Colour: Predominantly velvet black with a striking red tail fin

Sexing: Telling the difference between the males and females is difficult. They only difference known is the females tend to have a more rounded abdomen. It is impossible to sex juveniles.

 Personal Review

Ernie… well, Ernie is our Redtail Shark. He was not my choice of fish, he was my partners. As a way of trying to get him involved with the hobby, I told him he could pick a fish… Along came Ernie.

Ernie is not my first Redtail, and he won’t be my last. I honestly think these fish get a bit of a bad rap for no reason. Over the years I have had three Redtails and not one of them has caused any kind of issue with any fish they have been kept with.

I keep Ernie in a mixed community tank (see stocking list) and the only fish it has a bit of a chase around with is my Golden Algae Eater, even then the chasing works both ways and it isn’t very often. They will often cruise the tank together quite happily.

Redtail Shark Cave
Redtail Shark Cave

Ernie is difficult to photograph as he is shy, as soon as you approach the tank he darts into his cave (pictured). It is his cave, and no one else is allowed in it, but he happily shares the caves near it with everyone else in the tank, including the Cherry Shrimp! It doesn’t take long for him to forget you are there, but you have to stay still enough and not approach the tank with the camera apparently.

I personally didn’t follow any of the guidelines with adding him, he was added about mid-way through stocking the tank and I keep him with fish they are supposed to hate, but he has been in there for about 8 months now and never caused any issues. He was added when he was about 2.25″ long, and is now about 3″.

Ernie is the only fish in the tank that has a name, I think that in itself is quite telling. He is interesting to watch and his striking look adds something special to the tank. He is always busy, he loves to clean the leaves on the plants and thinks nothing of flipping himself up-side-down to clean every last bit of algae in the tank.


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