Algizin P works fast to destroy blanketweed – results can usually be seen within 1 week! Waterlife’s popular Algizin P product is a true algicide (as opposed to an inhibitor), and as such it is registered with the HSE. Algizin P is blanketweed specific, it will not harm oxygenating plants, lilies, marginals or other aquatic plants. Algizin P is also safe with fish and filtration. Repeat use during the growing season every 4 to 6 weeks or when re-growth occurs.