Inert ceramic material with open-flow architecture and largest usable surface area Higher efficiency relative to conventional media, efficiently treating NH4-N and NO3-N. Most technically advanced bio-filtration substrate. 2kg box. The surface of the spheres is microporous and each Bio-Sphere has up to 54cm squ surface area for the establishment of bacterial colonies. It is suitable for the growth of various microorganisms and forms a stable and highly active bio-film on its surface. The three-dimensional void (3D) formed by the spheres produces a powerful bactericidal effect. They are a great base for sponge growth, micro-fauna and coral frags. Bio-Filter Sphere wil work in sumps, trickle filters, wet/dry filters, hang-on filters or directly in the tank. It can be used in both fresh water and seawater environment.