u could still do both. just go pick a ac500 sponge up use it with the airstone and the sponge u got on the filter . u can never have to much filtration
They are not the prettiest thing in a tank, but my old work (large freshwater wholesaler) now uses them exclusively, I've seen some HUGE bioloads handled with them. Great for growout or hospital tanks. It basically takes the sponge filter concept, and turns the tank into one gigantic sponge filter. Leave it to the Germans.