Algae blooms are natural phenomenon, when silt decays it releases Ammonia, The algae is natures way of stopping this Ammonia from killing the pond/lake/sea or what ever. When Ammonia is produced, Micro organism's feed on it including algae. these organism's then die off and Nitrite is produced as they decompose. This Nitrite is then eaten by other organism's, When these die off Nitrate is produced, This Nitrate is then consumed by yet more organism's, When they die off Nitrogen is produced, Nitrogen is a fertiliser. As it gathers on the bed of the the water it fuels new weed growth. This is th