taken from wikipedia
An adult rainbow shark thrives in a 55 gallon sized tank with water at the neutral pH range (6.5 to 7.0 pH), with temperature kept between 22 to 26°C (72 to 82°F), and water hardness maintained at 2 to 15 dH. A single rainbow shark is normally mixed with other community fish of similar size
Rainbow sharks are compatible with barbs and rainbow fish, which are upper-tank and middle-tank dwellers. They can also live with danios, loaches, plecos and gouramis. Also they can live with bala sharks
Rainbow sharks are tank-bottom and aquarium-surface cleaners. Being bottom-level and mid-level dwellers, they consume leftover fishfood. They are known to be territorial, and aggressive to their own species. If kept with their own kind or relatives, harmless play-fighting occurs. This fighting behavior involves head-and-tail butting. Provision of hiding places and hollowed decors such as plants or artificial cave-like and tunnel-like aquatic ornaments minimize this typical behavior. Due to this behavioral characteristic among its own kind, rainbow sharks are not recommendable to the new aquarist. Keeping them with relatives such as red-tailed sharks, and black sharks are avoided