API Phos-Zorb for the API Nexx and Rena SmartFilter selectively removes ammonia, nitrite, and nitrate from freshwater and saltwater aquariums. It also removes phosphate, a by-product of fish metabolism and decaying organic matter and an additive in some tap water supplies, aquarium products and filtration media.
Size 4 - Fits API Nexx Filter & Rena SmartFilter
Size 6 - Can be used on any aquarium filter for aquariums up to 55 gallons
Directions: Each pouch is effective for up to 2 months. Change regularly for maximum effectiveness.