blackout length without killing coral & nem

[reef bound]

I did a blackout for 3 full days with no ill effects on my corals or fish, however I did not have a nem. I added about an hour of lights each day for a week then went back to normal. This was done in a red sea max (34g) and no water changes until the 3 days was done. I was unsure if I had dinos or red slime algae and this took care of the issue, so was still unsure. (Didn't treat with anything-- just no lights)
I believe niloc16 had done something like this a couple years ago and when his dinos died it gave his tank a bit of a crash. Might be worth looking back in the archives here to check it out. Hope it helps.