Directions for use The amount required will depend on stocking densities and amount of food added to the aquarium. For heavily stocked tanks, use 3ml to every 1lts of aquarium water and for aquariums with lighter stock loads, add 1ml to every 1lts of aquarium water. For best results, use Nitra-Guard BIO-Cubes in a denitrator reactor and commission the denitrator as specified by the manufacturer. If the BIO-Cubes are to be used in a filter bag or reactor, place them near the protein skimmer to assist in removing the nitrate and phosphate rich biomass faster. After 1 to 2 weeks, the bacteria colonies will become prolific enough to start lowering nitrate levels in your aquarium. If nitrate and phosphate levels in your aquarium are high, some cloudiness may occur which clears in a few days. Soak BIO-Cubes in freshwater for 24hrs before use. For detailed step-by-step installation, go to our support page.