This is what I use and I'm very far from being a "big breeder".

Babies up to 500g can stay in a 6qt if they are still eating and doing fine. Juvies can stay in a 15qt up to about 900-1000g if they are eating and doing what they should. Adult males and younger females(1000-1500g)all end up in a 32qt unless they are smaller adult males(adult hypo @900g), then they are in 15qts. Most adult females are in 41qt tubs, unless they are shy then they get 32qt tubs. I have some females who are over 2000g in 32qt right now and they are fine