Your a brave soul. From what I read about salt tanks, proper filtration is the biggest push. Sorry to hear about the power outage messing up your tanks. What problem put an end to you run? Loss of lighting?
Combination of things. One major stress was the temperature -- it was like 104 degrees after the storms, and the corals have a pretty narrow thermal range. Fish didn't like it either. Probably the next biggest stress was no water movement, meaning low oxygen. More of a problem for the fish, but corals do rely on water movement so that sediments don't settle on them and irritate them. No light -- corals depend on light for their nutrition. So everything combined was just too much.
One reason I was able to get away with no filtration is because I kept small tanks, less than 50 gallons. My filtration was totally biological -- lots of "live rock" and sand. The filter I currently run on my planted tank is just some sponges and the little ceramic rings -- yeah, I'm catching more of the fine debris and cleaning it out monthly, but really what you're doing is creating more surface area for bacteria -- biological filtration. You could achieve the same thing by creating more area in your tank to perform the same function.