I keep all my adults in 28qt tubs. Granted I don't have any over 2,500g yet, but I've had no problems breeding in these. I even had good locks from a 800g male x 1,100g '05 female in a 12qt tub. They all eat, shed and breed perfectly, so I see no reason to go bigger at this point. Balls seem to do better for me in cozy spaces. I still keep my juvi cal king in a large tub, and any new species would get the most appropriate floor space and height in it's enclosure, but balls are pretty good that way.