Long time lurker, first time poster

I have an RES in an ourdoor pond in Maryland/DC area - and I just wanted to make sure I had all my bases covered to let him brumate over the winter! Here are my details for the pond:
-About 6500/7000 gallons
-4 Feet Deep throughout most of the pond
-1 large drop waterfall (about 3 feet off rock ledge) and 2 smaller/runoff type water falls
-Pump currently runs 12 hours a day for the waterfall, but once it freezes I either run it 24/7 or I'm thinking about getting aeration pumps to save a little money but still pump some oxygen in there and prevent freezing surface
-Lots of big gold fish - maybe 30 or so and a handfull of misquito fish/baby goldfish
-decent leaf/muck on the bottom
Full Pond:
Waterfall:
Main Waterfall Feed:
I've come out the last few days to clean out the skimmer/pump housing and found my RES lazily floating in the skimmer net! It's a little alarming because we lost on RES last year to getting stuck in the same area

Am I overlooking anything to help the process out? The turtle is about 6/7 inches round and was a pet store purchase - but has been in the pond for about 6 months.
Any insight/concerns are welcome - thanks for taking a look!
-D