Q: What is phosphate?

A: Phosphorous is an essential element for plants and animals. Phosphorus, measured as phosphate (PO43-), enters the aquarium from fish and invertebrate waste and decaying organic matter, such as dead algae and uneaten fish food. Water treatment facilities may add phosphate to tap water to prevent pipe corrosion and reduce concentrations of heavy metals in drinking water.

Q: Why test for phosphate?
A: While phosphate is required by fish and plants, too much phosphate can lead to cloudy water conditions. In saltwater aquariums, phosphate precipitates dissolved calcium (Ca2+) and magnesium (Mg2+) ions, inhibiting the growth of hard corals and other reef-building organisms

Q: What level of phosphate is safe?
A: While phosphate is not harmful to fish, the phosphate level should be zero in saltwater aquariums and freshwater aquariums, including those containing live plants. The phosphate level in a new aquarium will depend on the purity of the water used to fill the aquarium. Phosphate level in tap water can vary daily depending on the treatment process used. Phosphate tends to accumulate in established aquariums.

Q: I have a high phosphate level. What should I do?
A: In a freshwater or saltwater aquarium use API’s Phos-ZorbT. Phos-Zorb is a filtration material that removes phosphate. Making partial water changes can also help reduce the nitrate level, especially if the initial phosphate level is very high. However, because many tap water supplies contain phosphate, it can be difficult to lower phosphate levels by this method. API’s Tap Water Filter will remove pollutants, including phosphate, from tap water, making water changes effective.