I have to little "doctor fish" Dunno what they are, they are blue and very tinny and attach to other fish to eat of bugs. I have one that likes to swim INSIDE and attach to the exaust of my powerheads. Untill it clicks on and blows him out, they are on about 3 mintues cycles. After it turns off , he will go back in and repeat. It'd funny watching a fish shoot out a powerhead. Dumb fish. dumb dumb dumb, but funny. he used to prefer attaching between the glass and rubber suction cup on my heater, but it's moved to the sump. so no he's go for the powerheads.