Bring the world's most exotic reefs into your home with CaribSea's Arag-Alive substrates. Beauty and brains, Arag-Alive helps maintain a proper pH for the life of your aquarium without the constant addition of chemicals, and creates a biological balance to discourage nuisance algae. The quick clearing Arag-Alive contains millions of bacteria per pound specially engineered for aggressive waste reduction. It is engineered to suppress new tank syndrome and compress the ammonia cycle. The 20 pound bag of Hawaiian Black has a typical size between 0.25 mm and 3.5 mm and features an average density of 80 pounds per cubic foot.