The nitrifying process of bacteria is the most important phase in Nature Aquarium filtration systems. In this process, toxic ammonia or nitrous acid are decomposed and become harmless nitrate. BIO-RIO is a mixture of porous filtration materials, each with its own unique function. Volcanic rock has a large surface area, ideal for the propagation of aerobic bacteria. Kikou Rock contains various minerals and diluted trace elements and serves to activate the water. Japanese Oak charcoal absorbs acidic substances and further promotes the colonization of beneficial bacteria.