Calcium and carbonates are the two most important elements in seawater, which are required in relatively high amounts and they have to be added separately through Colombo Calcium+ and KH+. Colombo All-Four contains all other macro and micro-elements that corals need for an optimal growth and a perfect colour development, like magnesium, iron, iodine, potassium and many more. Based on the Calcium test, you add Colombo Calcium+. Add 50 ml Colombo All-Four for every 100 ml of Calcium+ you are adding to your tank