Will need a 75 when full grown. As far as "normal feeding" that is all the owners opinion, as well as the diet they feed them, so it could vary, also it would depend on how big the fish allready is. Basically, there is no set answer, but I would expect to most its adult size within a year if kept properly (then slowly getting a little larger and a little wider after that).
also for future reference, this should be in the Central and South American Cichlid section.