Alkalinity question

[kien]

calcareous organisms such as LPS and SPS corals require ALK and calcium to build their skeletons. Alk typically is consumed at a greater rate so as Mike said it typically depletes first. If your alk isn't dropping (much), that probably means you are replenishing it via water changes at a rate equal to or greater than the rate at which it is being used up by your corals. There are any number of reasons why corals will consume more or less Alk. For example, If corals are happy with ALL other parameters such as light, low nutrients, flow, etc, they may be in the mood to grow lots and thus may take up these trace elements. Some corals will grow every slowly and thus will consume Alk and calc very very slowly. Of course, the number of corals (per volume) you have in your system is a factor as well.