Why do rainbow sharks need so much space?

Why do rainbow sharks and even red tailed sharks need so much swimming space? I know that they never stop swimming just like sharks do but it seems that they are small fish and don't have a large bio load? could you get away with having an albino rainbow shark in a 20 gallon long or a 30 gallon tank?

 

well they do get to 6 inches, which isn't much to sneeze at.
you could put one in a 30, but really the preferred size is around 55.
they get large and aggressive, so make sure you have a cave or log for him
per

 

They do not swim all the time like real sharks, they tend to hide a lot in caves, if given the opportunity. Yes, you could put one in a 30 gallon, but it will at least attempt to kill any other resident in that tank. They are highly territorial and have a large territory, which is why it is recommended for at a minimum a 30 gallon, as that is the footprint of their territory. 20 gallon long would work for a single shark by himself but as they are fast swimmers, a 4 foot tank is really ideal.

 

55 because they are territorial. They won't feel as cramped there. I've certainly noticed the difference in my rainbow shark.

 

Rainbow and Red Tailed sharks are sold when they are juveniles.

My LFS had a mature Rainbow Shark. He was 6" but was husky. Beautiful fish if you have a large tank to keep them in because if they feel cramped they get unhappy.

I have also had both but not at the same time. Kept them in my 125G 6' tank and they loved it. Always were out and about.

 

It's crazy how ideally, they should be placed in at least a 55-gallon tank. Here in our city, there are petshops that put rainbow sharks in a 15-gallon tank and there are about 30 of them!!!

 

It's crazy how ideally, they should be placed in at least a 55-gallon tank. Here in our city, there are petshops that put rainbow sharks in a 15-gallon tank and there are about 30 of them!!!

That's just very short-term, and because most of the shops don't have the space.