you want flowing alage growing in your tank? if that is what you want, then you could take some rocks you like and clean them. put them in a shallow dish of your tank water and put it in the sun so it grows alage. put it back in your tank and point powerhead at it and maybe get the same effect. not something i would care to do but hey, to each their own. there might be some plants that might give you the same effect but i'm not a planted tank kinda guy to know the answer to that one.