Most, if not all zoanthids are very easy beginner corals. Some do require a little more or less light in order to keep their colors, but it's all something you kinda have to experiment with. I have about 50 different varieties, and I don't doubt that there are much more than 250. I wouldn't suggest allowing them to grow over clams or scallops, as they will eventually cover it to the point where the mollusk wouldn't open fully. Zoas are very peaceful, but they are capable of growing over corals and other things and can basically smother things by taking all the space and light. Any zoa or paly can live in harmony together in the same environment, but once again, certain ones might grow faster and smother the others. The only ones to avoid has to do with personal preference (if you don't like a certain type or color, you wouldn't want them taking over your space). They receive most of their nutrition from the light, but do filter feed on phyto and zooplankton, and the larger palys will even eat meaty foods. I've heard that they can benefit from strontium and iodide, but it is not necessary, and proper water changes with a good reef salt or crystals will give them all the nutrition they need.