Phosphates are one of the primary contributors to the growth of algae in an aquarium. The presence of the materialized form of any type of phosphate is known as ortho-phosphates. Ortho-phosphates are created by the breakdown of simple and complex organic phosphates and are major contributors to the growth of algae. High levels of phosphates not only lead to algae blooms, but have even been thought to have a much greater impact on algae growth than nitrates. Although phosphates generally arenít considered detrimental to the health of your fish, levels higher than 1mg/L can lead to unsightly algae outbreaks.
Phosphates are introduced into your aquarium in many ways, even your tap water may contain phosphates. Other sources of phosphate include, but are not limited to, pH and KH buffers, carbon, fish food (and overfeeding) and even salt. Phosphates can even be generated within your aquarium through a heavy fish load, dead plant matter, undigested fish food in waste and even the dieing off of algae.
In order to get a handle on phosphates, sources of phosphates need to be identified and eliminated (or reduced) and phosphates that are already present in your aquarium need to be removed.
Examine everything from fish food to salts and make sure that they contain little or no phosphates. If a product does contain phosphates, try to find a phosphate-free alternative. Make sure you are not over-feeding your fish or feeding them an inappropriate diet. Uneaten or undigested food is a source of phosphates.
Phosphates can be removed from your aquarium through good maintenance. Provided your tap water doesnít have extremely high levels of phosphates, frequent water changes are your best bet to reducing phosphates. Unless you have strong currents that keep debris from settling on your substrate, youíll need to vacuum thoroughly to remove any waste and uneaten food. Frequent water changes should not only keep phosphate levels down, but your fish will also appreciate the clean water.
Another method of eliminating phosphates is through the use of phosphate-absorbing products. These are made by various aquarium product manufactures and can be added to your filter. Most of these require good water flow. When using them, make sure you read and follow all directions. Since some of these products generate a lot of heat when initially placed in water, make sure you wet them before adding them to your filter.