Per the instructions on the bottle, use 2 ml per 25 gal of water everyday. I have a 50 gal tank and I use 4ml everyday. I have been dosing for almost a month and haven't seen any new GHA growth on powerheads and on rocks and seems like existing GHA on the rocks is slowly browning out. Also the Phosphates are staying under 0.02 using a Hanna Phosphorus Checker.