Tetra - TETRA BIO FOAM GRID 304060Tetra Whisper Bio Foam Grid replacement kit. Bio Foam provides an extreme amount of surface area for optimal biological filtration in the Tetra In Tank Whisper power filters. The Bio-Foam Grid fits the Whisper In-Tank Power Filter. Each Whisper Bio Foam Kit includes foam and a plastic frame. For best results replace the Bio Foam Grid according to the manufacturers recommended maintenance schedule. Bio Foam and Grid - PF 304060 For use with Whisper 304060 Power Filters.