did not control algae over five weeks of use. left alone with this additive the algae would have increased. i change water once a week with RO water and have two filters on a 48x15x18 tank. test strips show water is low in natrate with no nitrite. now going back to esha product which does seem to work.
i have not used these before and found it fidly to fit. on a walk with back of camera rubbing against my coat it came off. one corner started to peel and would not fix against the screen. one on my old compact camera has proved to be more robust and lasted for years..