shakaho said:
What will be the temperature range in your garage through the winter?
Depending on outside temps, it is usually in the mid to low 40s, sometimes in the 30s, but I can't remember anything actually freezing in it. While it's not heated, it is attached, and has a well-insulated garage door. It's on the opposite side of the prevailing winds. I've got a min/max thermometer in there now, and if temps get too low, I could run a space heater in there for a while.
I visited my local pond store today, and the woman was very helpful. She recommended an external air pump and an air rock (?). I already have some large containers that I can use. At first I thought it might be cruel to put the fish in a rectangular box, but they are already spending most of their time in the skimmer, and that has a lid on it and is smaller. I should use the pond water, and stop feeding them.
This has a couple benefits over the heater idea we'd been thinking about. First, I think it will be a lot cheaper to run the pump rather than a heater. Second, we won't have any worries about the heater damaging the pond liner. Third, we can turn off the pond pump.
She also told me that my new pond only needs to be 24" deep to be able to keep goldfish outside next winter (our frost line is about 18".) Twenty-four inches is exactly the same maximum depth my local city ordinances allow for unlicensed and unfenced ponds.
And best of all, she gave me the idea of hiring a couple high school boys next summer to bust up the cement apron under the pond and dig the holes. Much cheaper than the landscaping guys!
If we keep the waterfall in the same place, and expand the perimeters a bit, I calculated a 24" deep pond would hold approximately 525 gallons. Still small, but a big improvement over the measly 50-60 gallons I have now!