How do you protect fish in your winter pond? The winter temperatures have dropped into the single digits and I worry just a little about our beautiful fish in the big pond.
There are three threats to fish in winter–scavenging herons and raccoons, and cold temperatures. I almost didn’t see the big heron this morning standing right next to the pond. My parrot was screeching her predator warning, but it took my eyes a minute to adjust to the sight of a huge white bird standing perfectly still and blending in with the snow. Luckily the fish are hibernating under the large, flat stones we’ve placed in the pond, almost invisible except for the tip of a tail.
Protect fish with deep water
To protect fish, the depth of the pond is at least 3 feet. This depth provides enough space for the fish to go to the bottom where the water temperature is somewhat even. And even if the surface of the pond freezes, the ice won’t affect the fish. Next, we’ve placed large flat stones just below the water surface to provide hiding places and hibernating places for even the biggest fish. Heron’s can’t get their beaks under the stones and the fish can see the birds shadows staying safely out of reach. Even raccoons won’t get into the deeper water to get under the stones.
I’ve seen fish inserting themselves side-by-side in the holes made by the bricks holding up the flat stones. I think it provides them some security and some additional warmth. In the fall as the temperatures become cooler, we cut back on the food we give them once a day. This lets the fish know to begin their hibernation process. By the time the really cold temperatures hit, they are fully protected.
Protect fish with moving water
Sometimes though, the temperatures are so cold, if we didn’t keep the waterfall flowing, the fish would really be in trouble. We can’t protect fish if they have no oxygen.
When ice covers an entire pond for long periods of time, it doesn’t allow gasses from decomposing litter to escape. This in turn, builds up in the water pushing out the oxygen. We’ve been able to keep our pond healthy and protect the fish in even the worst cold temperatures with two methods. First is to keep the waterfall flowing and on the coldest nights we’ll add a trough heater. The trough heater is typically used in horse and cattle troughs and puts out just the tiniest bit of heat. It doesn’t make the water so warm that the fish come out of hibernation. But it prevents the ice from forming solidly in the temperate water surrounding the heater.
We’ve become fairly attached to our fish. It was heartbreaking to lose one at the first part of the winter, but we’ve had most of them for about 15 years. We’ll have to refresh the pond with a few new fish next spring, but we can relax the rest of the winter knowing we’ve done our best to protect them now.
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