FHM, HSB, HBG, and RES are the only fish inhabitants.
Esshup just posted some O2/temps for his Indiana pond and the water was getting down to 34 degrees F.
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=501500#Post501500I don't have any experience with O2 readings and don't know what fish are in his pond, but just looking at the water temps...34 degrees F is so close to freezing (assuming 34 is acceptable) that monitoring the temps and catching it in time to change the aeration schedule would be difficult with such a small window beteen his 34, your 33, my 36 degrees and actuall freezing.
My gut still suggests that keeping a small hole is marginally effective, but also low risk in potential harm considering this areas lack in ice coverage and extended cold weather.
