The only filters I know of that can go anaerobic in power outage are canister, UGF and FBF. Canister is a closed system and can go anaerobic quickly if you let the media clogged up. Here is an incident reported by a reknown aquarist:
HOB, biowheel and wet and dry can never go anaerobic because they are open system to the atmostphere. HOB carries so little media that it has no capacity to create an anaerobic zone. Biowheel and wet-and-dry are semi submerged systems that the media will go dry in extended power outage.
let it be known though that canistors and FBF's have some very good benefits. IF you have frequent power outages (more than 4 hours) then you may not want one. I never had a power outage that lasted more than a second.