So I have got a red tailed shark from a friend. It has been in a 40 gal tank for around 6 months but the tank was ill kept and over stalked. He asked if I wanted it and I said I would take it.... I as well have a 40 gal tank but want to take better care of the little guy. I was wondering if I keep the water clean, and feed him well will he be able to reach full size or once they have some stunted growth are they stuck at that size?