Q. I purchased an orange cup coral or sun coral from my local fish store without knowing much about the species. They fragged my piece off a larger colony. The orange cup coral or sun coral does not seem to be acclimating very well to my aquarium and the polyps are almost never open – even at night. When I check my temperature, ammonia, nitrite and nitrate, all measurements are normal. My aquarium is 1.024 and my other corals seem all right. Do you have any ideas as to what may be the problem?
A. As you may know, orange cup or sun corals are common even on Caribbean reefs. These bright-orange corals possess even brighter orange/yellow polyps, and look like a fiery sun when all of their polyps are open. This, combined with their encrusting nature, has made them a popular species in the home aquarium. Orange cup coral or sun coral (Tubastrea faulkneri) is a large polyp stony coral (LPS) from the family Dendrophyliidae. The name Tubastrea is broken down from Latin: tubus, meaning tube, and astron, meaning star. The name likely reflects the skeletal structure of the coral, which is like a tube, and the polyp at the tip which is shaped somewhat like a star. Often in the wild you will find orange cup or sun corals upside down near the entrances of caves or within sunken ships. This position serves two purposes in that it helps the animal trap planktonic food and also prevents debris such as sand from accumulating on the coral.
Unlike many popular large polyp stony corals, orange cup or sun corals lack the zooxanthellae algae that provide the corals with much of their energy in the form of sucrose. Large polyp stony corals that need reef aquarium lighting are often considered easier to keep than orange cup or sun corals mainly because they do not require the constant feedings their non-symbiotic cousins do. Orange cup or sun corals survive in areas of the coral reef where sunlight is dim by feeding on zooplankton. These corals, when hungry or sensing food, will release their tentacles in hopes of trapping particles passing by in the water. Many people purchase orange cup or sun coral for their home aquariums under the impression that it’s a light-demanding coral like most large polyp stony species offered for sale. The aquarist is often shocked when the orange cup or sun coral never opens up and just slowly withers away.
In order for your new coral to thrive, it will require feedings at least twice per day. I know many aquarists who have had good success with orange cup or sun corals feeding them once in the morning and once in the evening; though many report that orange cup or sun corals usually feed at night. There are many zooplankton diets for corals available at fish outlets and small artemia (baby brine shrimp) would also work. You may want to watch for your coral’s polyps to appear, but it is likely once the coral senses food it will open up. Remember to turn off all filters, pumps, or anything that would quickly remove the food from the water. The only thing to leave running when feeding the coral is your water circulation powerheads or wave maker. I would recommend leaving filtration off for at least one hour to ensure the coral has had ample time to capture some of the free-floating food.
Another thing to keep in mind is that it is often necessary to feed each individual polyp separately. The reason for this is that if several polyps do not get enough food from the water part of the colony may die off. Once the coral loses flesh, algae can begin growing on the coral. In the home aquarium this can smother the entire colony. To target feed often times a pipette or syringe works best. There are even several specially made target feeders on the market that function well.
Overall, orange cup or sun coral is considered to be difficult to keep. Though in my opinion, when cared for properly, these corals can thrive in the aquarium. Often aquarists assume, given their bright colors, that they are symbiotic corals not unlike other large polyp stony coral species and fail to properly care for them. Sadly, many fish store attendants also fail to inform customers of this coral’s unique needs and requirements.