To make a long story short recently my boyfriend and I took over a 50 gallon salt water tank that my father has owned for the past 9 years or so. We upgraded it to a 75 gallon tank, had and RO unit installed in our home etc etc. When we took the tank there were only 4 fish (a fox face, 2 clown fish, and1 skunk clown fish) and two very random corals. One was a leather mushroom, the other is some sort of polyp coral (possible star polyp?). The tank was in pretty critical condition when we acquired it. My father is old and couldn't keep up with the tank for the past couple of years, so he was thrilled when he learned that would take it off of his hands and give everyone a happy and healthy home. The water went from toxic waste, to crystal clean with perfect water parameters, a brand new sump, and as I said now RO water for water changes and top offs. Everything was great for the first few months, the two existing corals were thriving more than I had ever seen before and the fish were very active. We added a few more corals to the tank and a six line wrasse. We are taking things slow. However now the polyp coral that was originally in the tank seems to be having some major issues! I've lived with this tank under my fathers care for a while, and I've never seen it have this issue! As far as we can tell the fish aren't messing with this coral, and there's no other corals close by that can sting or attack this particular coral. I'm attaching some images with this thread so you can see what the coral is starting to look like. Most of the polyps retracted in and its becomes pretty bald right in the center of it! If anyone knows what's going on, or has any suggestions that would be greatly appreciated! It would be a shame to have this coral live its entire life in terrible conditions and then suddenly die in the new set up!