IceCap's Bio-Sphere is a powerful arrangement of small ceramic spheres contained within a sturdy and compact ball measuring 1-1/4 inches in diameter. Each ball, weighing 1KG, can provide up to 18 gallons of efficient biological filtration for both freshwater and marine aquariums and ponds. The high surface area of the media promotes the colonization of beneficial bacteria necessary for efficient nutrient cycling. Perfectly suited for use in various filter types such as sumps, trickle filters, wet/dry filters, hang-on-back filters, and in aquariums. Dimensions: 1-1/4in Sphere. Each box contains 40 Bio-Sphere Balls.