Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Installed as media in a Canister Filter

Filled the bio-denitrator tray and has been actively helping keep the water crystal clear. The media has been in use now for about two months. It's expected life is about one year out of the box. If more than one box is used the media may last longer. It is one stage in a five stage canister filter. The other stages include active carbon filtration, fibrous screening Mattes, 400 watt UV bio filter, and a chemical balancer removing phosphates, etc... 100% of the tank's water passes 67 times an hour through these filters.