Don`t forget that some of the aerobic bacteria could die if you dont get the power back "soon". Your canister/sump could possible turn in to a toxic bomb if it takes too long... this of course depends on how many hours we are talking about, and what "state" your canister/sump is in.
If we are talking several hours i would feed carefully the next days after power comes back, and i would also kept an eye on the water parameters.
If we are talking several hours i would feed carefully the next days after power comes back, and i would also kept an eye on the water parameters.