Mine rarely put their tentacles out during the day. The best time to feed them is at night. Wait at least an hour after the lights go out. Then drop a little food in the water. It will help encourage them to extend the tentacles. Wait another few minutes and then feed them. Also, favias, favites, closed brains (pretty much all the same) do better lower in the tank. The don't need tons of light. Good luck with it. Looks very nice BTW.