Method of controlling water surface inhabiting pests

A buoyant slow-release composition for locally targeting a floating photosynthetic microorganism bloom in an aquatic system, the buoyant composition comprising a photosynthetic microorganism inhibitor, a binding agent, at least one swelling agent and a solid floating agent,

• wherein the solid floating agent is selected from the group consisting of cellulose derivatives, ground plant biomass, saturated hydrocarbons, resinous materials, foam, wax and natural or synthetic latex;
• wherein the photosynthetic microorganism inhibitor comprises an oxidizing agent;
• wherein a concentration of said photosynthetic microorganism inhibitor is between 0.005 g/m2 and about 50 g/m2 of the surface of said aquatic system;
• wherein a concentration of said oxidizing agent is between 0.5 ppm to 50 ppm;
• wherein said composition is adapted to locally release said inhibitor into water in said system to contact and oxidize said bloom;
• and wherein said buoyant slow-release composition is adapted to move together with said bloom in said aquatic system.