Red Sea Coral Colors A B C and D supplements contain the 31 minor and trace elements present in the skeleton and soft tissue of all corals. A – halogens I2 Br F2 B – potassium and boron C – Fe and 7 complementary metals D – 18 bioactive trace elements. The elements in each supplement are related by their biological function and are associated with the production of specific color pigments pink red green/yellow and purple/blue in the soft tissue of stony corals. All 31 elements are required by all stony corals irrespective of the actual color the coral displays. For best results in displaying coral colors use Red Sea s NO3:PO4-X as part of the complete Reef Care program. Coral Colors A B C and D should only be dosed according to a measured requirement of the aquarium. Comes in a 4-pack of 100-ml that supports a 250-liter SPS aquarium for approximately 60 days enough time to witness impressive growth and a darkening of coral pigmentation.