Definitely a bummer!
While I have only skimmed over most of the responses, I’ll have to say my old tank breached on one of the seams. Huge mess and flooded part of the basement.
I went to Walmart and bought 30g plastic bins for about $12 each, relocated everything to the garage floor, and used powerheads and air bubblers to keep oxygenating the water. The bins were in the garage for about 3+ weeks while we cleaned up the mess and ordered a new tank. I used no heater and no chiller in the garage (Summer in the Northeast) and water temps ranged from 74-86F. I suspended lights over the top of the bins using egg crate to suspend the light fixtures and alternated the lights on cheap timers between the bins every few days (corals can last days without lights just like long storms with clouds).
Corals (soft, LPS, SPS), fish, and major inverts like shrimp all did well, however I did loose a few minor inverts like snails/hermits. Don’t spend a lot on high end plastic bins as cheap ones worked well. Bungy cords were used to keep them from expanding on the long sides due to water pressure in the plastic bins.
To make things worse, we were on vacation during this mess, but fortunately we had some friends watching our home who quickly took action to keep the leak in check and save the water to pump back into the leaking display from the refugium.
Bottom line:
1) DON’T GIVE UP!
2) Use water detectors.
3) Have someone monitoring your tank roughly once per day or every other day while you are gone.