There are few corals that can stand up to the brilliant colors of the members of the genus Tubastrea, which are known as orange cup corals or sun corals. The most commonly encountered species in the aquarium trade have orangish pink corallites, and bright orangish yellow or white polyps. If you look back at the aquarium literature on the members of this genus, you will find they are considered to be very difficult to keep. But this coral will actually thrive and even reproduce in captivity if you are willing to devote the time to feed them.
Difficulty: The sun coral is non-photosynthetic — that is, it does not harbor zooxanthellae. All of its nutrition comes from ingested food, namely plankton. The key to keeping Tubastrea colonies alive is to feed the polyps daily (some people have had success with this coral by feeding them several times a week, but they grow and reproduce more if fed more frequently). If you feed the sun coral smaller meals three or four times a day, the polyps will open more during the day. Feed your sun coral a meaty food, such as finely chopped frozen seafood, frozen fish eggs, chopped frozen mysid shrimp. By alternating food types, you can assure that the polyps continue to open more fully. You can squirt food among the sun coral polyps with a turkey baster. In most cases, the polyps open to feed at night, but if you schedule feeding at the same time every day, the sun coral polyps will begin to open at that time as they await a meal.
Physical description: The sun coral has a skeleton that is orange, orange-yellow or red-orange in color, while the polyps are usually bright yellow (it is referred to as a sun coral because of the yellow coloration). It usually grows in round clumps. They have relatively large polyps that are usually retracted during the day and open after dark.
Range: Tubastrea species are found in subtropical and tropical coral and rocky reefs around the world. The sun coral is found in a variety of reef habitats, but most often occur in shaded areas of the reef (on pier pilings, in crevices, caves, under overhangs).
Compatibility: The sun coral does not have sweeper tentacles and is generally pretty peaceful toward its neighbors. An adjacent coral will have to contact the tentacles of the sun coral polyp to receive potential damage from its stinging cells. This coral is eaten by a specialized snail called Epitonium billeeanum. It is yellow and orange and blends beautifully among the corallites of its prey.
Aquarium conditions: The sun coral can be kept in aquariums of various sizes, but it tends to do better in smaller aquariums because it is easier to feed. In fact, the sun coral makes a great coral for a specialized deepwater aquarium that contains some fish from deepwater habitats (these types of displays are becoming fairly commonplace at public aquariums). The sun coral also is not dependent on bright lighting to survive — thus, lighting selection is not a factor. Water movement should be moderate to strong. Water parameters for the sun coral are: calcium 400 to 450 ppm, alkalinity 3.2 to 4.8 meq/L and no phosphates. The Tubastrea corals also tend to grow best at lower water temperatures (between 74 to 78 degrees Fahrenheit).
Care considerations: Handle your Tubastrea as little as possible, as rough treatment can damage the polyps. Do not place the sun coral near a sandbed, especially if you keep sand-sifting gobies, as sand that collects on the colony will cause tissue death. If sand gets on your sun coral, blast it off with a jet of water. The sun coral is also sometimes smothered by hair algae, but if you keep it in shaded locations, this is less likely to occur. Another problem faced by Tubastreakeepers are Aiptasia (glass) anemones. These noxious little cnidarians tend to do best in aquariums that are fed often – exactly the situation we find in the sun coral aquarium. These anemones can sting and damage Tubastrea tissue.
Breeding: The sun coral will spawn in the home aquarium, and the asexually produced planula will attach and grow. If kept in optimal conditions, they can overtake a medium-sized aquarium in a couple of years. Some of the more branching forms can be fragged by breaking off a section.