If you have any kind of an algea problem, you'll want to correct it first.
Frequent feeding is also a must for the non-photosynthetic varieties, and doesn't hurt for the photosynthetic ones either. Oyster Eggs and Cyclopeeze a pretty good mix, and some will accept Phytoplankton as well.
Good strong water flow through the fan is also important.
The real trick is feeding them enough while still keeping water chemistry in good shape.
Not impossible, but trickier than alot of corals.