Calcium carbonate derived from marine aragonite is biogenic (created by living organisms) and naturally re-occurring. Protect the reef by using this superior and sustainable product. Add these marine accents to any saltwater or Cichlid aquarium for spectacular effect. Each piece of fossilized aragonite and shell is a one of a kind natural sculpture. These unique accents will complement any reef structure and are recommended to be placed in the forefront of an aquarium And scattered around at random intervals.