Hello Jason Why not just set up each 15 gallon with its own sponge filter? I don't understand the need or desire for have a single filter running all three tanks. If it's to save on electrical costs, then having one large air pump running the 3 tanks would do the same, if you're looking for basically the same water conditions in each tank, by using your tap water with the same water changes on each tank should give you the same water conditions in each tank. If there are other reasons for wanting to try this could you let us know and then maybe I could suggest something different or at least understand your desired effects. John ------------------------------------------------------------------------- This is the apistogramma mailing list, apisto@listbox.com. For instructions on how to subscribe or unsubscribe or get help, email apisto-request@listbox.com. Search http://altavista.digital.com for "Apistogramma Mailing List Archives"!