I have the same scenario. I think Im going to take my DBT's out of the big aquarium until theyre a little bigger (above 2 inches) and stronger. Then theyll be able to swim in water that deep and with fish that are more powerful. They also get caught in the filters water stream and have a really hard time getting out of it. Im going to put them in a 10 gallon with only 3-4 inch of water for a few months.