While traveling (which I do weekly as my job) I had a house sitter/pet sitter watching the house, feeding my cat and feeding my fish etc. I trained him up well on the tank, things to look for etc, to check all connections twice a day and report any problems immediately, along with an emergency number to my tank service guy. Well he came in one morning, all was fine with the tank (it looked great at that time BTW, everything was flourishing), then came back that evening to feed my cat and checked on the tank. All the snails had fallen off the glass/rocks and were dead, my starfish (bristle and serpants) were mush and all the corals had mushed out as well. When he called I had him check the pumps and when he put his hand in the sump ZAP.. what had happened was a RIO pump I had feeding my fuge froze and burned up.
That experience cost me everything in the tank except my fish. My service guy arrived 30 mins after the call and declared the tank DOA. He spent the night pulling everything out, rock into a garbage can with PH and heater and transfered my fish to a smaller tank I had then drained and refilled the display.
That was about a 2 years ago now.... once we put the LR back in and re-seeded, I had a non-stop battle with Hair Algae and cyno that no matter what we did we couldn't get rid of it.
Soooo.. I broke it all down again, cooked the LR for 6 weeks without lights and high temp, installed a new DSB. That was 4 months ago now and am happy to report that the LR has started to come back (I purchased some new pieces to re-seed) and no hair algae in sight, though I do have some small patches of dynos that are slowly going away. I am now able to keep shrimp, snails and star fish, cukes etc... and just put in a couple of new pieces of coral, a 10" wall hammer and 5" frogspawn that appear to be doing well.
While it was a very expensive and time consuming ordeal, it has had a plus side. I now have a rock lift that supports my LR 1" off my DSB so I have full efficiency in the tank now and the picking and choosing of the LR to put back in has made me much happier with the rock scape. It also encouraged new equipment, I no longer skimp on pumps and such. I now own tunze and a mag 12 to run the flows.
Unfortunately the risk still does exist that a crisis will happen while I am out of town, but I feel much more comfortable now that I have top grade equipment and backups.