My fish family has been in some frigid temps (as low as 22F) lately
and without benefit of a water change for 2-3 weeks. I'd like to give
them a small water change but wonder about the efficacy of the
chemicals needed to make the county water safe. It's going to get up
to 45F today, going down to low 30's tonight. Thoughts?

N. Virginia
2300 gallon above ground pond, pump off, heater in, air stone on, 3
small koi, 4 small GF