Increase the bio-capacity of your Nexus system by simply adding more Kaldnes media. Kaldnes Moving Bed process creates an oxygen rich environment, with an even distribution of water throughout the media, thus avoiding dead areas normally associated with static type media. Totally maintenance free and self cleaning. Sold in 50 litre bags (50 litres = 1.8 cubic feet). For exposed installations, cover your Nexus with a custom fit lid.