if your already properly filtered a powerhead would pretty much just add flow to your tank, bigger fish like a bit of a current, thats what I use one for, a bit more water movement because my bigger fish like it. you can also run undergravel filters, and some other sorts off them too....like a round foam filter....although thats not much benefit...some can also airate your tank....or you could just have your power head sucking in your own air bubbles....