I have a 72g with 90 lbs liverock which is about four weeks old. Water parameters are excellent and right now I have a yellow tang, two damsels and a bunch of snails in it. I also have a Mushroom Coral. I have a 65X4 PC light and have two maxijet 1200 and one Seio 650 gph for the waterflow. I keep the lights on for nearly 12 hours a day and the coral looks great with lots of colors. If I switch off the lights, within like 30 minutes, the coral starts shrinking. Is this normal?