Crystal Bio is a unique, eco-friendly filter-media, heated in excess of 900‚Â°C, creating a hyperconnecting glass cell structure. This produces media with a surface-area at least 10 times greater than most plastic alternatives. Furthermore, the weight is extremely low in comparison to other porous filter media: 50 litres of Crystal Bio weights 7,5 Kilos! Attention: Crystal Bio floats! ADVANTAGES: - Crystal Bio media has an Inter-connecting porous cell structure allowing for a massive biological surface area. - Crystal Bio helps prevent pH drop. - Helps reduce Nitrates - Suitable for multi-bay filters and trickle filters.