if the light , the water pumps and the power heads gets shut down ( a blackout for example) ., how long can a fish or an invert or a Coral live ... can you be specific cuz i got many many types of corals and fish.
Depends. If it's cold the water will cool down quickly which will cause problems. Things would be fine for a week or so without lights, but you need heat and some sort of circulation after a day or two.