Re: New set up

>Don't turn off your undergravel filter, Do not.  When you turn off your
>undergravel, all that nice bacteria dies due to the lack of fresh oxygenated
>water reaching it.  This may 'crash' your whole tank.  If you are using the
>airstone and pump method on the undergravel, think about switching to
>powerheads (which create currents but no massive bubbling).
Umm, can anyone explain what powerheads are?