I have been using Aqua Medic Antiphos in a Aqua Medic Phosphatfilter for more than a month now...lots of algae... last week, I added a bottle of Aquapharm Sorb-4 and the algae problem is not as bad as before... this is a new product, so have yet to be tested in the long term... but I recommend you to give it a try... it's a lot cheaper than Rowaphos. Bought mine from AM.