FAQ: I thought phosphates were bad and could lead to unwanted algae growth. Why would I want to add it my aquarium?

This is true, but only when phosphorus levels become excessive, that is, when there is more phosphorus available than the plants can use. When this happens, it becomes available to algae. Phosphorus is still vital to plant growth, though. Flourish Phosphorus™ should be used in cases where there is a phosphorus deficiency.