Dennerle Nano AlgenStop is a highly effective phosphate remover for nano fresh water aquaria.+ removes the main cause of algae infestations -phosphate+ fast-acting, active for up to 3 months+ binds phosphate permanently+ excellent bio-compatibilityMode of use for Dennerle Nano AlgenStop:Recommended dosage: 10-20 ml for 10 l of aquarium water. Pour required amount into the Nano FilterModule or the Filter Extension, then rinse thoroughly with tap water. Replace after 3 months or when the phosphate content rises again.