Filter Floss Bio-Media is ribbon type material commonly used in our Aquafalls pond filters in place of lava rock. Pond owners have found that Filter Floss is better than lava rock since lava rock is high in mineral content and is very heavy. Filter Floss is a flat strapping that is embossed on both sides creating additional surface area for bacteria. Filter Floss Media is lightweight, will last indefinitely and has no effect on water quality. Pond builders installing our Aquafalls filters will find it easy to convince customers to upgrade to this media since each media bag in the filter will weigh only 4 lbs. instead of 40 lbs. if filled with lava rock! This makes cleaning much easier! Each box fills two mesh bags.