Gas cans are fine, as long as they're new, of course
Calcium,
alk,
pH,
nitrate and
phosphate are the biggies to test for. Even calcium and alkalinity aren't as important as they would be if you had stony corals (SPS or LPS).
All the corals you listed are primarily photosynthetic, and get all they need from light. There's some speculation that xenia can absorb nutrients from the water as well, but none of your corals will readily take, or need prepared foods.
If you have a question about anythig you add in the future, let us know and we'll do our best to let you know if it requires feeding.
