Advice Please

I need some advice from the experts. We've gone from summer into winter
here in Idaho (zone5, used to be 4.) I've successfully wintered over the
fish for 3 years using a couple of airstones. This year I decided to use
a bit more, 2 airstones, an Oase pond aerator and a small 300gph pump
for some circulation. (none at the lowest level) My question is, am I
overcirculating? Temps are wildly varied and I'm worried about the fish.

Pond is 1800 gallons
2.5 feet deep with two chimney tiles for the fish to 'hunker down in'

TIA for any/all advice. This is one weird fall (or lack of) Nightime
temps are forecast at 3, 8 and 15 degrees for the next 3 nights, highs
in the 20's/30's. Just don't know what to do at this point. Open areas
are still there, just the 'COLD' temps are a worry now.

deanna