i keep leopard frogs so it's a different situation. i do weekly partial water change (between 1/3 to 1/2 volume), checking for stools periodically about 2x a day. i've also got a filter running a ton of aquatic plants (java moss, crytocprynes, etc) so that does help with ammonia levels. i dont actually do a total cleanout just this kind of maintenance. I should say that i siphon the gravel pretty well so that's probably why i could get away with doing it this way.