Q: I have two small fish ponds that are connected. One is three feet deep and the other is about a foot deep. I have a pump that circulates the water between them. In cold weather, should I run the pump or leave it off?
A: During the winter, fish have few needs. They sink to the bottom of the pond, quit eating and slow down their bodily processes. They do need oxygen, however, and that is where your good judgement comes in. If temperatures are not severe and the pond is unlikely to ice over, you can turn off the pump or pull it out and store it. If the pond freezes over occasionally at night but thaws during the day, you have little to worry about. If it looks like the pond will be frozen for several days, you’ll have your work cut out for you.
If the pond has a thick layer of ice on it, gently pry up the edge of the ice sheet and crack it into pieces. DO NOT use a hammer to crack the ice as it lies frozen. Water doesn’t compress but fish do! To the fish down below, hammer blows to the ice are the equivalent of hitting them with the same tool. They won’t survive your pounding. A simple way to avoid this is to buy and use a pond heater designed to keep a small area of water melted. Leaving the pump on continuously could also help prevent icing but you have to be careful that splashing water doesn’t freeze outside the pond and eventually drain it dry.