depends on what your wanting... A powerhead would be better for some applications, but i think air stones look fake and take away from the natural look of the tank. What fish are you stocking? A powerhead would probably be your best bet, but i dont run one in my 150 because the two canisters keep the surface agitated enough... If the surface of the water isnt moving, you will need something to help with the oxygen exchange... What kind of filter is it?