I came home early this morning from a week at the in-laws. I arranged with a neighbor's son to take care of my menagerie while I was away. Even though he has some experience, there were last minute changes that had me leaving before the guy was in town and staying longer than originally planned. I did leave him very detailed instructions and double checked everything was in order before I left. I also turned off the MH's to help keep evaporation down as I anticipated top-off would be the most likely area for failure plus it would help with the algae problem I've been battling. Anyway I came home around 4 am and went to sleep. This morning I checked on everything and all the animals were well and alive but I found that the water level in the reef tank was 2 inches too low! I checked the sump and found it nearly empty with the pump running dry and most of the live rock exposed. I checked the ATO resorvoir and it was filled. I unplugged the pump from the ATO and plugged it in directly and it was working so somehow the float valve ( autotopoff.com ) failed. I dont know what happened as it has always worked fine. I didnt find a snail stuck in there and the valve was moving freely when I pushed it with my finger. I dont know when this happened but it had to happen a few days ago due to the condition of the tank. I lost just about every stony coral - LPS and SPS - in the tank, including a really great monti plate that has survived and recovered every previous disaster. I havent yet seen my purple firefish, flasher wrasse and one of the nematodes gobies. The pistol shrimp was found dead. All the tubeworms in my sump and DT are dead. The softies - zoas, leathers, 'shrooms - are looking in bad shape but most seem to have survived, excpt for the my hairy mushroom and rhodactulus. I wont know the full extent of the damage until the lights are on for a few hours but it doesnt look good. I dont know if I should just take a leave from the hobby but my wife is pushing for it. I understand where she is coming from as I've spent much money and time on this tank and just now managed to get to the point where I was happy with the way it was running. I had some algae problems to tackle but the fish were and corals were all established and thriving. I used to ask how others would leave the hobby after something went wrong rather than just restart but now I understand. It is really depressing.