Can i use a powerhead on my goldfish fry tanks undergravel filter?
NO! Do not use a powerhead on your undergravel filter while you have fry! Fry like to hide in between gravel, and if they are small enough, the suction below the gravel will cause them to be stuck which will kill them. Never use an under gravel filter with a powerhead if you have fry under 1/2 an inch.