Hey guys, I have the same 28 gallon bio cube for 5 years. It has been a fish only tank until a few days ago. Learning about corals has revitalized my love for the tank and I was super excited to get my first corals lately. The day the corals came, an Alk test came as well. It is the Red Sea Alkalinity test. I am getting a reading of 16! I have never tested for this, and everything seems fine. In fact, 2 of the zoas I got have already opened all their polyps. What can I do to lower this? I do not know if this is a recent problem, however I did switch salt recently. I am now using instant ocean salt. I made sure to premix and heat my water for around 14 hours before the change.