For a few years I worked in a field of the urethane foam industry. Furniture, bedding and drapery foam are OPEN cell foams and things like insulation foam are CLOSED cell foam. The chemistry is basically the same at the macro level but there are differences and those differences dictate whether a particular piece of foam will be closed cell or open cell. Closed cell foam will not provide the desired filtering effect in aquarium applications because its surface area is not high. Open cell foam, on the other hand, works well in aquarium and other filtration applications because it possesses very high surface area for the beneficial bacteria to live and function. I'm not familiar with Poret foam in detail, per se. I've seen pictures and read articles and seen the data indicating it's a very efficient material for aquarium filtration. I know it's highly open cell in nature based upon pics and videos of water being poured through it so rapidly. It appears to be a ceramic like foam material. Like Ron, I would stay away from any open cell urethane foams that contain additives intended to control bacteria, fungi or other micro-organisms. Many of these additives are toxic to aquarium inhabitants.
