Reminder Of The Day:
If you are home when a power outage occurs, then just like you would manually try to oxygenate your tank, you would also take the screen out and set it in some water (even tap water in the sink.) Problem solved, no damage. It can sit there for two days with no ill effects. You could even put it in a shallow pan of water outside in the sun, where it will probaby grow
If you are not home, however, it becomes a question of which you lose first, your screen or your whole display. Long term (days) you are going to lose both, so we'll look at short term (hours). Somewhere in-between is the question: If you are not home when the power goes out for 2, 3, 4, 5 hours, etc., then how much of your screen will you lose, and how much of the nutrients will be "released" back into the water?
Well, most screens are designed to be up and out-of-contact with the water, so there will be zero "release" of nutrients during the power-outage. And floating screens that stay in contact with the water will not die or release nutrients at all in a short-term outage, because they stay wet. So immediate release of nutirents is not a factor in any situation.
The real question is long term loss of filtering, i.e., how much of the screen will die off during the outage. When you get back home, the screen has been drying for a few hours, but is still moist. What you do is put it in your sink with water and give the dead parts a chance to fall off. Not sure of how much time is needed, but just do a regular cleaning of the screen every few hours until it seems that most of the dead stuff is removed. Doing this in the sink will prevent any nutrients from getting back into the tank. You then put the screen back into operation, and it's no different than if you just did a regular cleaning. And this is the worst case.
I myself unplugged the wrong plug once and left the screen 6 hours with no flow. The fan was still on, but the lights were off at the time. It was all still moist, yet a bit hardened. I did not think at the time to remove the outer layers of dead stuff, so I just put it back into operation right way. What happened was the next day or two there was a very slight increase in N from zero (clear Salifert) to a very slight pink; probably got up to about .5 or 1. P did not ever increase, however. And this was without properly removing the dead stuff. So overall, I don't think power outages are really that eventfull for scrubbers.