I'm not an expert by any means but I'll tell you what I do with mine. I have my in a 29G tank with MH lights. I've had it in several different places in my tank. Have you seen the Koralia Nano powerheads? They have the suction cups with the magnets so that the suction and the magnet holds on each side of the glass. Well I took 2 of those and used superglue to glue my sun cups to one side of them. Now they can go anywhere against the glass in my tank and I can remove them easily without injuring them for feedings. I feed them often, at least every couple of days. I also feed them what I feed the rest of my tank, homemade fish food. Most of the time, I'll take them out of the tank, put them in a measuring cup with some tank water and feed them in there. I usually do this after I feed my tank so that they are ready and so that when I put them back in the tank the other animals don't climb over the sun corals to get their food. My sun cups are open more often than not. I bought them from saltwaterfish and got a combo of orange and yellow, very nice but nowhere near as beautiful as it is now. The lights don't seem to bother my sun cups, though I do keep them toward a corner but certainly not sheltered. I move my powerheads often and haven't had them get irritated because of flow.
With permission, I've kidnapped my friends sun cups and am slowly nursing them back to health. They aren't protected from the light or waterflow either and are looking much healthier. I've been feeding them when I see them out to encourage them to be out and open more often and I think it's working.
