I dont know how long, better to ask henward that since his is 'adult'. His one is at a foot, but I have seen them up to 20inches. I think his took him 2 years? I feed it hikari stuff, massivore, shrimp occaisionally. Mine is growing quick, noticable difference in size and colour, hes about 15cm now, got him at around 7-8cm. Will post pics again soon I think, just internet going slow :an!gry