Meet the new 4-part Complete Reef Care, providing hobbyists with more convenience at no extra cost, and ensuring optimal coral growth and vivid colors with only one test per week!Our long-term research has revealed that in most reef systems without refugium, the Major, Minor, and Trace elements and even the Alkalinity components are used up in a relatively fixed ratio. Since Calcium is the key indicator of coral growth, the 4-part program revolves around a single weekly measurement of Calcium, which determines the dosages of all 4 parts. The new Complete Reef Care is available in 3 sizes, to fit all system sizes. It is formulated so all 4 parts are used up at the same time, and if supplemented via Red Seas ReefDose, the hobbyist needs only to set their Calcium dose and ReefDose does the rest, which is super convenient. The new Complete Reef Care is chemically identical to Red Seas original 7-part program and provides the same great results, however, systems with refugium should use Red Seas 7-part RCP to properly maintain all elements. Medium contains 1x 1L Calcium & Magnesium, 1x 2L Alkalinity & pH stabilizer, 1x 0.5L Iodine & Potassium and 1x 0.5L Iron & Bioactive elements. Medium suitable for aquariums up to 300L