I guess I am the exception to the rule have used purple up on all my tank start ups and have had great success. You have to remember to seed the rock first and then the purple up will work. It does not contain coralline it just boosts it. I have personally seeded hundreds of pounds of rock with it and have never experienced a problem. I had a mishap on my new 300 gallon reef when I was on vacation my son dumped a bottle in my tank a freaked emailed Carib-Sea my phone number told them what was up. They called me back with a hour and told me everything would be fine. I cannot remember exactly what they said, but the iodine was what I was worried about but I tested as they recommended and never saw a spike. They told something about the type of iodine they use in it but cannot remember what. Guess I am getting old. LOL Anyway that is my 2 cents worth. LOL