Aqua- teck Filter... rated for a 10-15 gallon...
DO NOT BUY!
ITs an over achiever!!! Normally this would be a good thing... However when the suction is so powerful it sucks young fish to it... and makes a current so strong it whips some heavy set fish around like feather waites.
To buffer it, you need a WHOLE sponge the kind you use for a car shoved into its spill way.... to buffer suction... you need a whole soda bottle ( about a liter) and poke very small holes in it... within ten seconds the water in the bottle is gone and its chocking.... Can use the cut off neck going down to the bottom either... The basket useless.... That and it still even with a full sponge in it whips horn wort around the tank like it in a slow moving washing machine.
It recently sucked up my anlge fish ( of course she poor girl died, because there was nothing I could do for it after it got sucked up, she had swimbladder which didn't help matters).
She was too weak being young to be able to pull her self off the basket, so I used the bottle neck to the floor.... the filter sucked her up under the bottle neck and up into the filter.....
HInd sight being twenty twenty... I should have gone with the ten gallon mini filter that aerated too.... At least I could buffer it.