Here Comes the Sun (Coral)

Many people think of corals as “plants” or “flowers;” it’s easy to do, given their brilliant colors and generally sessile nature. However, corals are animals, and while some are photosynthetic (like plants), many are carnivorous–including one of my favorites, the sun coral (Tubastrea sp.):

16B11 Sun Coral at night

Sun corals belong to the group known as “large polyp stony corals” (LPS for short), which means that although they have strong internal skeletons (largely composed of calcium, like bones), they are not reef-building corals. Instead, they attach themselves to rocks and construct their colonies on pre-existing surfaces. 

I started raising “suns” because although they have a reputation for difficulty, they’re actually fairly simple to keep alive, if you’re willing to meet their needs. First and foremost: they need to be fed, and they prefer meaty foods like mysid shrimp. Fortunately, they don’t mind eating frozen food (defrosted, of course), and will learn to open and extend their arms for feeding when they sense food in the water. (They also learn approximate “feeding times”–mine open regularly at 10am and 7pm, just in time for feedings. Like many animals, they can develop a fairly accurate internal clock.)

In the wild, sun corals are generally nocturnal, possibly to prevent fish from nipping their long, delicate arms. Since my reef has no predatory fish or other species to harass them, the sun corals have learned to open during daylight hours also. They don’t even seem to mind too much when the hermit crabs try to steal their dinner:

16B11 Crab with Sun Coral

The coral gets its name because, when open, it looks like the sun, with its mouth at the center. If you look, you can see the mouths (they look like slits when closed) on every polyp:

16B11 Sun Corals (pink)

Sun corals reproduce in two different ways. Each adult polyp can clone itself, budding off  genetically-identical individual polyps from its sides and base, and the colony can also reproduce sexually, by sending out a spray of genetically unique planulae. Although true spawning is rare in captive systems, I’ve been fortunate enough to have it happen several times in my reef, resulting in a number of “accidental” colonies, spawned from the “parent” sun coral at the center of this photo:

16B11 parent sun colony

The coral on the upper right is actually a child of that parent colony, as are these baby suns growing underneath my filter intake:

16B11 suns under intake

Many public aquariums culture sun corals, and train them to open in daylight for the benefit of visitors. They’re showy, and among the brightest specimens on any reef. Sun corals actually come in numerous colors, including red, orange, yellow, and black (or green):

16B11 Green sun

Sometimes, you even see multiple colors within the same colony (though it’s rare) — look closely, and you’ll see a single black polyp and a yellow one on the lower right side of my newest colony:

16B11 Sun

The black polyp sits just underneath the orange “head” immediately to the left of the yellow one, if you’re having trouble finding it.

I love sun corals because they’re brightly colored, responsive, and interesting to watch. They can be time consuming to feed, mainly because it’s helpful to put the food directly into their arms, but to me the benefits make it worth having all the extra hungry mouths to feed.

Have you ever seen sun corals growing, in the wild or in an aquarium?