Stop Algae by Starving It of Phosphate Nuisance algae and cloudy diatom films thrive on the phosphate and silicate building up in your water. Left unchecked, they smother rock, glass and corals no matter how often you scrub. PhosGuard rapidly removes phosphate and silicate from marine and freshwater aquaria. It is highly porous for high capacity and bead-shaped for optimum water flow, so it works fast without clogging. Unlike an exchange resin, it does not release anything into the water and will not leach phosphate or silicate back, and controlled testing shows no detectable soluble aluminum released under reef conditions near pH 8, keeping even soft corals unaffected. PhosGuard is developed in-house by the chemists at Seachem Laboratories, the science-driven company founded in 1979 in Madison, Georgia. That chemistry-first approach is why PhosGuard is engineered to be highly porous for high capacity and effective removal, binding phosphate and silicate rapidly without leaching them back into your water. Pre-wet PhosGuard in a double volume of freshwater, then rinse it before use. Place 85 mL (1/3 cup) per 200 L (50 US gallons) saltwater or 400 L (100 US gallons) freshwater in a filter bag, in high flow but not tumbling. Test phosphate or silicate after 4 days and replace only once levels climb again. Take back control of your algae. Add to cart. What It DoesPhosGuard rapidly removes phosphate and silicate from marine and freshwater aquaria. It is not recommended for phosphate buffered freshwater. It is highly porous for high capacity and bead-shaped for optimum water flow. PhosGuard is not an exchange resin and does not release anything into the water; it does not leach phosphate or silicate back and may be removed, dried, and returned to service until exhausted. Controlled experiments show that under reef conditions (pH near 8) there is no detectable soluble aluminum released from alumina, and even at three times the dose soft-bodied corals such as Sarcophyton remain unaffected. In comparison testing PhosGuard (Alumina Oxide) binds 0.87 mg/g PO4, PhosBond (GFO and Alumina Oxide hybrid) binds 1.19 mg/g, and PhosNet (GFO) binds 1.41 mg/g. DirectionsMay generate heat on initial contact with water. Pre-wet by adding to a double volume of freshwater, followed by a rinse. For best results, PhosGuard should be rinsed before use and placed so as to maximize the flow of water through it but not so that it tumbles against itself in flow. It may be used in a canister filter, media chamber, box filter, or any high flow area of a trickle filter. Use of a filter bag is recommended. Use 85 mL (1/3 cup) for every 200 L (50 US gallons) saltwater or 400 L (100 US gallons) freshwater. Leave product in place for 4 days, then test phosphate or silicate concentrations with either MultiTest: Phosphate or MultiTest: Silicate. If the concentration of the component you are trying to decrease has not dropped to around 0.02 mg/L, then replace the PhosGuard, otherwise leave in place until levels begin to climb again. As long as concentrations remain under control, the product is not exhausted. Over treating is not recommended. Continuous use of small quantities is better than intermittent use of larger quantities. Available Sizes100 mL, 250 mL, 500 mL, 1 L, 2 L, 4 L Why Seachem PhosGuard Attacks algae at its source: it rapidly strips the phosphate and silicate that nuisance algae and diatoms feed on, in both marine and freshwater aquaria. High-capacity, high-flow design: it is highly porous for high capacity and bead-shaped for optimum water flow, so it works quickly without clogging or channeling. No leaching, reef-safe: unlike an exchange resin it does not release anything back into the water, and controlled testing shows no detectable soluble aluminum under reef conditions near pH 8, leaving even soft corals unaffected. Filter-flexible and reusable: it works in a canister, media chamber, box filter, or high-flow area of a trickle filter using a filter bag, and may be removed, dried, and returned to service until exhausted. Best ForMarine, reef, and freshwater aquariums battling nuisance algae or diatoms driven by phosphate and silicate. Especially suited to reef keepers who need a fast, high-capacity remover that will not harm sensitive soft corals. Not recommended for phosphate buffered freshwater. FAQ How long does it last, and can I reuse it? Leave it in place and test phosphate or silicate after 4 days; as long as concentrations stay controlled the product is not exhausted. Because it does not leach anything back, it may be removed, dried, and returned to service until exhausted. Where does it go in my filter? Rinse it and place it in a filter bag in a canister, media chamber, box filter, or high-flow area of a trickle filter, positioned in strong flow but not so that it tumbles against itself. Freshwater or marine? Both, at 85 mL (1/3 cup) per 200 L (50 US gallons) saltwater or 400 L (100 US gallons) freshwater. It is reef-safe but is not recommended for phosphate buffered freshwater.