Coral Complex 2 180 caps. Coral Complex 2 by Coral Incorporated. Coral Incorporated Coral Calcium 2 is the original (1999) powdered coral capsule in the USA. The formula has become the most popular and successful coral capsule formula in the USA. The formula has remained unchanged because it works so well. The most notable additive is 400 IU of vitamin D3 as cholecalceriferol in each capsule. Vitamin D3, the sunshine vitamin is necessary to charge the receptors in the small intestine that are instrumental in the uptake of calcium.