API Prevent Algae Liquid - 237ml, 118mlAlgae - the bane of our lives! It ruins ornaments and gravel, clogs up the filters and covers the sides of the tank... it has to go! Unfortunately algae build up is just a natural part of having an aquarium. However this fluid actively removes phosphates from your aquarium which will dramatically slow and control the growth of Algae - so having a pristine tank will be much, much easier. Also helps to prevent green water.