The Two Little Fishies PhosBan Reactor 150 and Two Little Fishies Little Reactor Adjustable Height Filter Plate is for use with soft media. The Adjustable Plate has a gasket that holds the plate into place. This is useful with soft media that you do not free floating as the Reactor will grind the media. Soft media examples are carbon, Purigen and resin. The Plate comes with a sponge.