As someone already alluded to, you will need to float a heater on the surface. The danger in a frozen pond is two-fold. First and most obvious, if the pond freezes solid, the fish will most likely freeze solid also resulting in its rather unfortunate demise. Second, a pond that freezes over does not allow gases from rotting detritus (oooh, maybe I shouldn't use that word in this thread) to escape. The toxins, therefore, build up and poison the fish.Flower1982 said:I live in Pennsylvania and it does get pretty cold here in the winter sometimes. Tonight it's about 27 degrees outside. Sometime this week the low temp is going to be in the teens. I didn't want to take the chance of letting the goldfish outside during the winter and then have them freeze to death. I'm sure you think I'm stupid for caring about my goldfish to get a bigger tank for them just so they can be brought inside for the winter andfor not trying to winter them over in the 80 gallon containter pond.
An alternative: place a pot of water on the stovetop and bring it to a boil. Carry the pot out to the pond and place it on the ice. Remove it when the pot has melted through, forming a hole. This will allow gases to escape. If it is a large pond with a lot of surface area, create 2, 3, 4 holes in the ice.
The thing you absolutely DO NOT want to do is add any kind of commotion to the pond. Waterfalls, powerheads, pumps etc. only serve to disturb the fish and encourage them to move about. This is a bad idea with the water temperature and metabolism so low. The best thing for the fish is to remain as still and dormant as possible until the water warms up in the spring.
Just my .02