He has been in the tank since I bought it about 8 mos ago (one of my first additions). The tank had been up & running for well over a year when I purchased it. I had not done a water change in a couple of weeks (usually every week). Ckd water params 3 days ago & ph was 7.8, nitrates 10, ammonia .50 & alk slightly low. I freaked out, it has always been near perfect! After a 10% water change yesterday: ph: 8.0 (added reef sucess buff by red sea), alk: norm, nitrates: still 10, ammonia still .50, calcium: 420, specific gravity 1.022. I fed the tank & saw his arm over a rock & went to feed him & he didnt touch it. My cleaner shrimp soon came & took it. I touched him w/ my tweezers & he barely moved. The lights have gone out & he is still almost in the same place. Was the ph change that abrupt? I have never had a problem w/ it b4. Everyone else in there is fine ...so far. The only thing I have done different to the tank is target feed my corals (soft) lugals. I normally feed phyto feast (but only once a week).