BAH i am having loads of trouble getting the black sun to extend and its starting to lose flesh.
i have now decided to start removing it from the tank into a bowl and flooding the water with food, hopefully even if it doesnt open it will filter some food from the water.
It may be daft question but have you tried the half a pop bottle trick?
Were you cut a big pop bottle in half put it over the coral and introduce food through the lid put the cap back on and you can leave it for a fair time as the corals still in your tank ?
i do something close, i pop it into a bowl (without coming out of the water) and then put the bowl into a heated water bath (to maintain temp) feed the water then put into the dark.