Fluval BioMax is suitable for both fresh and marine aquariums. When used in the middle filter module Fluval BioMac is t he ideal host material for large populations of beneficial bacteria. They provide 50% porosity per volume. This is divided into 88% double opening passages and 12% single opening spores. This maimum usage of each rings usable volume offers surface areas of 7.2 m per ring - 1530 m/liter for thriving bacterial populations within and without the structure. The ring size and shape provieds an excellent strainer for large particulate wastes when used in the first (lowest) media module. There still is powerful activity when employed in the lower chamber as well. Fluval BioMax due to the epanded minute porous internal matrix will eventually become exhausted. Over time the pores clog up with non-decomposing waste material. Fluval BioMax requires replacement every 6 moths to maintain efficient biological activity