Many cyanophytes are important members of phytoplankton of stagnant and running waters, whereas other form thick mats in a wide variety of benthic habitats. Certain planktic species are capable of forming water blooms, which in summer months may colour the water in green, dark green or reddish. Cyanophyte water bloom is welcome in fertilized fishponds because of the production of biomass and oxygen, while in lakes using for recreation purposes (swimming, water sport and games) or water supply are sources of nuisance. Some cyanophytes forming water blooms produce toxins and allergic compounds into the water.