Foam has been widely used as a media for pond filters. Foam has excellent surface area for beneficial bacteria and is extremely effective when differing foam densities are used in the pond filter. Foam is also effective at removing suspended particles from the pond water.
The downside to foam is clogging. Tight foam catches too much debris and will clog rather quickly. Some pond filters require you to remove the foam and wash them off- messy!
OASE has designed filters that use foam and are very easy to clean. The new Biotec 5.1 & 10.1 pond filters are cleaned simply by opening a valve and raising the handle on each pad to clean it. Easy and fast! It only takes me about three minutes to thoroughly clean my OASE Biotec 10.1 pond filter! Speaking of clean, I haven’t seen a cleaner water garden than the one in my front yard.