Seachem PhosBond Phosphate Remover, 250 ml 250 ml size Use 60 ml for every 50 gallons of saltwater or 100 US gallons freshwater. Leave product in place for 4 days, then test phosphate or silicate concentrations with eith the Seachem MultiTest Phosphate Test Kit or the Seachem MultiTest Silicate Test Kit It may be used in a canister filter, media chamber, box filter, or any high flow area of a trickle filter. The PhosBand is already in a flow through filter bag