IceCap Bio-Plate Biological Filter Media is a compact brick form that contains a dense arrangement of small ceramic spheres, providing efficient biological filtration for up to 750 gallons in both freshwater and marine aquariums and ponds. Use it in a sump, trickle filter, wet/dry filter, hang-on-back filter, or directly in the aquarium. Plate dimensions: 8 x 4 x 3/4in. Contains one Bio-Plate (8in x 4in).