I used to have this cool pink sponge growing all over the place under all my zoas. It's all but gone now. My ornamental sponge has started to show decline as well, to the point I need to just throw them away because they are a lost cause. When I used tap water the sponge was the coolest thing in my tank. If I switch back to tap I might take a whipping for it, but I might try it just to see what happens.