Pond Temperature Swings

[confusion]

I have a pond outside (pics here) that I have some goldfish (sarasa, comet, shabunkin), and a few koi, along with a bunch of rosy red minnows. I have noticed that I lost about 3 koi over the winter. It is possible that they were picked up by birds.

we have been having a lot of wide temperature swings lately. 20F in the morning, and 60F in the afternoon, 75 the next day, then 40F the following day. The pond water pretty closely matches the outside air temp, with a few hour lag time. It has not frozen, as we don't drop below freezing for long enough. But, the fish are being exposed to 30F to 40F temperature swings in a day. That seems like it would be pretty hard on the fish. should I be heating the pond to reduce the temp swings?

The pond is about 2800G, but has a lot of exposed surface area for the size, due to the shallow river and waterfalls. Otherwise, I think the temp would be a bit more stable.

 

[rdd1952]

I'm not familiar with koi but my dad has had a goldfish pond (approx. 1000 gallons) in the back yard for almost 50 years and I've had one (about 120 gallons) for over 10. The fish are in them year round from single digit nights in the winter to 100 degree days in the summer and never lost a fish due to cold although I had to add an airpump to mine this past summer when we had 33 days in a row over 90 degrees. We have however, lost them to a huge owl and a blue heron. Some of the goldies we lost were over a foot long. Both ponds are now covered with mesh nets. So I would say it's quite possible that something like that did get your fish.

Because of the volume of your pond, I don't think you would see temp changes anywhere near that large during the day even if the air temp does swing that much since water holds temp pretty well. If there is a 40 degree difference in the high and low, I doubt your water temp would swing even half that.