Phos-X can be placed in a filter or just set directly into the water garden pool to absorb and trap phosphate, nitrite, nitrate and ammonia. This product helps reduce harmful nitrites, nitrates, phosphates and ammonia that may cause organic matter accumulation and foul odors. Excellent to use if you have fish. Keeps the water healthy. Treats 1320 gallons. Effective for up to 3 months. 0.8 Liters.