Specifically formulated for freshwater ponds, Laguna Phos-X Phosphate Remover reduces many of the compounds that encourage unsightly water conditions and foul odors. Phos-X absorbs and traps phosphate, nitrite and nitrate, gradually and safely.
As a result, your pond water will be crystal clear and provide ideal living conditions for fish and plants. Phos-X is easy to use and greatly reduces hands-on pond maintenance. Simply place one or more packs of Phos-X in the pond filter to maximize its effectiveness. 
2-pack, treats 5000 L (1320 U.S. gal.) of pond water for up to 3 months.

Other size available :
*  Laguna Phos-X Phosphate Remover, Concentrated Formula, 4-pack (PT571)