tim chandler wrote:
I'm in Memphis and our temps are just a bit colder than yours, although we
too are supposedly in zone 7, give or take. With a 1000 gallon pond, an air
bubbler hasn't been enough usually to keep the water from freezing over
completely once or twice during the season. But not thick ice! And if your
goldfish are smaller, they may not make it through the winter. I use a
thermostatically controlled heater, like a trough heater, at the bottom
about 2' down, just to keep the water above the freezing point. Even then
ice will form in areas away from the heater. I didn't lose any fish last
winter.

A 50 gallon pond that's in a raised bed, though, is subject to freezing more
easily than a larger, in-ground pond.

Yep, that's why it was hard to apply the winterizing tips I've read for
most ponds, they focus on the larger ponds. I started my pond and added
some small fish in July and now they are 3 to 4 inches long if you count
the tailfin, so still kinda small body mass. Pond is shallow at about
20" on the deeper end. I think I'll start out bubbling, but will be
prepared with an alternative if that is not enough. Thanks for all the
input.

You might be OK with just the air
bubbler, but a heater just to keep the water from freezing would certainly
provide better protection for the fish.

Tim C.