These clever tablets by market experts Nishikoi are designed to create optimum pond conditions. Each tablet contains millions of micro-organisms that lower the amount of nitrate in your pond to a level where algae & blanketweed struggle to survive. The tablets also contain another strain of microbes to digest pond sludge and fight against disease forming pathogens. Micro Clear is a natural, organic treatment and is not chemical-based. It is completely safe to use with all types of pond fish and plants. Micro Clear contains no heavy metals to control blanketweed growth. There is no need to turn off UV sterilisers when using Micro Clear. Furthermore, because it is organic it cannot be overdosed.