CaribSea Aragonite Seaflor Special Grade Reef Sand Is Ideal For Deep Beds, Plenum Systems, Reef Or Fish Tank Bottom Cover. About 1-2mm diameter. Proven to reduce nitrates. Provides calcium, carbonate buffer, Strontium, Magnesium, Molybdenum and Potassium. Discourages nuisance algae growth and promotes healthy fish and invertebrates. Controls nitrate, nitrite, ammonia and other wastes. Use at least 1 Lb. of CaribSea Argonite per gallon of aquarium water. For deeper sand beds, use 2 Lbs. 15 Lbs.