ULNS Phos is a complex inorganic phosphorous source designed to promote natural nitrogen uptake and nutrient control in ultra low nutrient systems which are phosphate limited. It provides an important nutrient source for nitrification and denitrification as well as proper nutrient assimilation. It is recommended for use by advanced hobbyists. Bleaching or coral tissue degradation may occur in ULNS systems where adequate nutrient content is not maintained. ULNS systems depend on bacterial management of nitrogen in a balanced carbon and phosphorus environment which allows rapid uptake of excess dissolved organic compounds. The conversion to bacterial biomass allows protein skimming to export unwanted nutrients that would otherwise build up in the system. This recycling of nutrients requires that all necessary nutrients, i.e. nitrogen, phosphorus, and carbon be present in concert. For maximum results, Continuum recommends that you use this product with BacterGen M, BacterGen MD or BacterClean M to keep microbe levels at optimum, along with Reef Micro Fuel to replenish and accelerate the growth aerobic anaerobic, and facultative bacterial populations. If nitrogen (or nitrate) levels are too low, then also use Continuum ULNS Nitro to boost them to the proper level. Caution, overuse or improper use of this product can promote unwanted algae growth!