I know they prefer it cooler than tropical, but what about low 60s, high 50s? I ask because I have a native darters stream tank, that would be perfect for them, and I want something to keep all the stream rocks somewhat clean. I can clean the glass but the rocks are a pain in the butt. In the summer than tank is low 70s, but in the winter it get much lower, maybe high 50s because it is in my basement.