Tubastraea micrantha, often referred to as the black sun coral is a really cool species of azoox LPS coral. Stunning bushy growth forms, black color, and large often fluorescent green polyps really make the black sun coral like something you wouldn’t see anywhere else. Relatively easy to keep in perspective to many other azoox corals, Tubastraea micrantha is non-photosyntehtic and does require frequent feeding of meaty foods.
Unlike other sun corals, the black sun coral also is more light sensitive and prefers higher flow rates. That said, black sun corals are usually considered more valuable than their yellow counter parts and are thus usually handled more carefully throughout the supply chain and often arrive in a better shape, increasing chances of success.
Although often described as black in color, Tubastraea micrantha is actually a dark shade of green and often has fluorescent green tentacles and mouths. If you’re really lucky, occasionally Tubastraea micrantha can even be found with a completely fluorescent green polyp, resulting in a seriously cool looking coral. Tubastraea micrantha is by some referred to as a tree coral, and is the only species in the genus Tubastraea with dendroid growth form.
In more simple language, it is the only Tubastraea that branches rather than the otherwise dome like (massive) growth. For this reason Tubastraea micrantha was thought to be part of the Dendrophyllia genus, and was actually described as Dendrophyllia micrantha as late as 1952 (Dendrophyllia micranthus var. grandis Crossland, 1952).
Like we mentioned before the black sun coral is non-photosynthetic, meaning that they do not derive the majority of their energy from light, instead relying on capturing prey as their energy source. In the wild this means that Tubastraea micrantha will hunt for drifting zoo plankton by expanding their polyps, stinging any zoo plankton floating by.
Captured food is then transferred to the manus of the sun coral where the food is then digested, nutrients are absorbed, and any waste is excreted. It is a cool process, but wild densities of zooplankton are hard to recreate in you system, unless you already have a automatic dosing system in place for your other non-photosynthetic corals. Luckily Tubastraea micrantha, and all azoox LPS for that matter, will fare just as well with large meaty foods such as mysis, chopped krill, chopped shrimp, chopped clamp etc.
In the wild Tubastraea micrantha are offered a feeding opportunity every night, so it is best to feed your sun coral as often as possible. We personally prefer to feed black sun corals daily for best growth and constant polyp expansion, but they will do just fine when fed two or three times a week.
Do keep in mind to feed less if you feed more frequently, since it is possible to over-feed Tubastraea micrantha. As a result undigested food can start rotting in the gut effectively initiating the death sentence. Over-feeding is not really a concern unless you really are feeding large pieces of meaty foods on a very frequent basis, but it is something to keep in mind. The baseline, just use common sense when you are feeding you black sun coral.
Sometimes Tubastraea micrantha can be hard to get to open up during the day, causing frustration to the hobbyist trying to figure out to feed their new addition. The main reason most incoming black sun corals are closed during the day, is that zooplankton is most densely available during the night, and from the corals perspective it is just a waste of valuable energy to keep the polyps open when no food is being captured.
Thus the trick is to make the coral realize that there is a meal to be had during the day. The easiest way to achieve this, is to feed any partially extended polyps during feeding time, but if even a single tentacle is not to be seen after a couple of days there are some other measures you can fall back to. Our favorite is the bucket method, which in essence is just putting the coral in a container and spraying it with “smelly” food.
The coral will smell the food and will often open up, allowing you to feed to coral. After a couple of times the coral should also start to open up while in the tank. It should be noted that while training your black sun coral to open up, it is always a good idea to feed it during the night to keep its strength up.