I have two tanks running, one grows coraline like crazy and the other has none. I bought both tanks second hand, both were well established when I got them. I recently finished putting everything I want into one tank. Lots of rock from the coraline tank into the one with none. We'll see if it keeps growing on the rocks. The parameters of both tanks are very similar. One major difference is the tank with all the coraline is dosed with BRS two part and the one with none is dosed with All for Reef. That's just what the previous owners were doing so I kept it up. The alk and calcium are the same. I don't hate not having to scrape coraline of the glass but it just seems like a healthy tank should have it?? I'm fairly new to all this and would love to hear your thoughts.