Hello friends, I have a 2 year old Duncan stays closed up in my main tank. When I place him in a quarantine tank he opens up. All other corals and fish are fine. Water is fine. I have a 46 gallon bowfront with 2 hangon back overflow to a 30 gallon sump, 5 gallon hang on fuge on the sump, skimmer in sump and lights for fuge I run when main lights are off. Is it being poisoned by other corals when they die from some corals growing over them? Should I split my Duncan? The 3rd photo is 2 years ago. Lighting by 2 Kessil's A360W Tuna Blue. The last 2 photos just taken of my Reef Tank. Been into salt for 2 years and fresh for 40. Looking forward to comments and ideas/suggestions. Also I notice a sheen of oil on the surface and I have been skimming one gallon every day for the past 5 weeks. Thanks. Anthony