An algaestat is a substance that is designed to stop the growth of algae by eliminating the algae food source.
What is an Algaestat?
An algaestat is defined as a component in a chemical which stops or prevents the growth and reproduction of algae. This is contrast to an algaecide, which is designed to kill algae. Algae are commonly present in freshwater, and the speed of algae growth generally depends on the amount of food available needed for them to survive. Thus, a way to battle algae is to deprive them of their food, effectively starving the algae of nutrients to grow and prevent a full algae bloom.
Algaestat treatments are chemicals which only controls growth of algae, not really killing them. One example is Sodium Bromide, which acts as inorganic algaestat. This algaecide supplies bromide ions to the pool water in order for it to be oxidized. Sodium Bromide also acts as a disinfectant which can be used for pool waters. This specific algaestat treatment is only applicable to pools which uses fresh water, and not for salt water pools.