Icecap Bio-Plate 8"IceCap's Bio Plates is a dense arrangement of small ceramic spheres in a durable and compact eight by 4 by three quarter inch brick form capable of providing biological filtration up to 750 gallons. The media's ultra high surface area is perfect for the mass colonization of beneficial bacteria required for efficient nutrient cycling in both freshwater and marine aquariums and ponds. Stack in a sump, trickle filters, wet dry filters, hang on back