Hi, I'm new to this site and relatively new at reefing. We have a 120g tank, set up since Nov. 09. Currently we have 3 175w MH, but are switching to LED/T5 combo as we have had poor color and growth overall. We have been having the worst time with SPS! Are chemistry is in line, at least with our test kits (Alk 8.0, ph 8.1-8.2, salinity 1.023, temp 77.2, nitrates 0 and Ca 450) but most of the frags we have end up RTN or STN after a week to several months. It all seems so variable. As soon as a show a sigh of relief thinking we've made it, it starts receding at the base. I have several right now that have lost tissue, but still have PE on the remaining tissue! This has happened to our birdsnest and pocillopora as well as the acro's, so I don't think it is a parasite. Any help/advice would be much appreciated. I am almost at the point of throwing in the towel. But, I am already addicted!