ok now last question... I've been thinking and trying to design an organic(?) filter system... you know how we have those water filters that have rocks, stones, pebbles etc etc, and you can drink from them? is it possible to create something like that for aquariums as well? or would that cause the water to become too hard / soft?
also i'm gonna go with a 60 x 30 x 30 for a community tank and hatchery, should 30 x 30 x 30 be enough for a breeding tank?