>Black sun polyps are a few levels of difficulty above the regular orange ones<
I wholeheartedly agree. They are much more likely to suffer from infections and die. They can be successfully kept, even fragmented, but it is not easy. I strongly recommend you keep them in an area of the tank with moderate to strong waterflow, perferably alternating in direction. Best if they are out of the light as well. And feed them often, with ground up seafoods, shrimp, squid, scallops, clams, etc.
When diving you will usually see these corals in areas with Very heavy current. They can grow to be many feet across.