on my refugium I have a light that sits on top of tank. well, it fell into the tank somehow and I found out too late. I turned it off and unplugged it but when I pulled it out stuff from the ballast went into the water. all corals closed up and shrunk I quickly cut off the flow from fuge to main tankand did a major water change.dumped most of the water from fuge and added new water. I also hooked up a hang on filter to the fuge with carbon. sump has 4 bags of carbon.I hope I saved everything. time will tell.