I recently ordered online some 1/4" thick black speaker foam. I have two AquaClear Quick Filters I am using as pre-filters for two powerheads. My plan was to use this as a thin outer layer in the filters over white polyester floss, primarily for aesthetic reasons to cover the the white floss. I did not notice before ordering the tiny type on the website that says "NOTE: Not for use in aquariums." This stuff looks just like sponge material for aquariums, only thinner. Does anyone know any reason why it can't be used in an aquarium? As long as it doesn't contain any anti-microbial chemicals, one would think foam is foam, don't you think? I contacted the company by email and they responded that it cannot be used as fish filter, but did not specify why. Does anyone know any reason speaker foam might be harmful to fish?