My tank has been running for a little over a year now and is doing very well. About a month ago I added a bunch of Zoa frags along with some Xenia. I really like the SPS stuff, and have been looking at them on Liveaquaria in the WYSIWYG section. My question is they are pretty much all labeled as "Difficult" on the care level. What is so difficult with keeping them? I don't want to spend a lot of money and then have them die on me.