Sun corals like ledges and caves, they do not like direct sunligh. I have six heads of suncorals (Tubastrea) and they all hide from the sun. They comeout mostly when the Actinics are on and the MH are off, and through the night.
This is what I got in my records for this type of coral. The Orange Sun Coral is a Large Polyp Stony corals (LPS) from the Family: Dendrophyliidae, Tubastrea, Species: faulkneri. The common name of Orange "Sun" Coral is misleading, since this is a coral that should be placed in low to no lighting with a medium current. Also, this coral lacks zooxanthellae, the microorganisms, which turns sunlight into food for corals. In the wild, Tubastrea are found upside down at the entrance of caves because their waters supply a very rich diet of plankton and nutrients. Due to the lack of zooxanthellae, this coral needs to be fed regularly, such as twice per day, however, it will depend upon the coral. When a coral is hungry or senses food, it will extend its' feeding tenticles. I feed small crustaceans and fish larvae, mysis and brine shrimp, chopped seafood and excess pods, cyclopeeze and golden pearl. You must feed every solitary polyp or else the colony will die from hair algae attacking its' weakened skeleton.
This coral will benefit from the addition of calcium, strontium, and other trace elements weekly to the water. These corals are a bright orange, and may not come out during the day, yet they are still very beautiful when closed. Some may be coaxed into opening earlier by feeding them. About 35 minutes before lights off, he is just starting to open up after having been fed.