Exactly which aquarium additives to use is a complicated question. However, all reef aquariums will need either calcium or kalkwasser (or both), supplements and buffer. Buffer is used to maintain pH. We recommend the Inland Seas Marine and Reef Buffer. You can use several types of supplements or just use a comprehensive formula such as the Inland Seas Biotrace, which includes Strontium, Iron, Iodine, Molybdenum, Vitamin C and B12, as well as other trace elements, vitamins, and amino acids.