Kent Marine Iron & Manganese supplements iron, manganese, potassium and other micronutrients to spur saltwater macro-algae and freshwater plant growth. Does not contain added phosphates or nitrates to cause undesirable algae growth. The iron and manganese used is chelated so that it stays in solution longer to provide lasting nutrient benefits to macro-algae, corals and freshwater plants. Shipping weight: 4/5 lb.