I got ice covering the ponds about 80% coverage a couple of weekends ago, when our temps were highs around freezing, lows in the teens F. I turned on the fountain pump in that pond, which bubbles just to the surface, to keep water moving and ice open. Skimmer and bog pump have not been shut off, still running. That pond is far warmer (shallower, too) than the koi pond, which had about 30% ice coverage yet this morning, and the temps this weekend have been really warm, today up to upper 50's and sunny. No ice on goldfish pond at all, still about 15% on koi pond. If that pond has an oxygen problem (it was brought up when fish in there died all of a sudden), then nothing has changed since summer, except that I added the fountain bubbler. I would think that would add to oxygen, not deplete it, right? I'm going to leave the fish alone, and just pay attention to how they act in the morning and following morning. All of the koi are under the ice, so I wasn't able to check to see how they were "sleeping" to compare. :cheerful:
And, I have no way to know if some bug was still alive to have jumped into the pond, but I doubt that, since it got really cold here weeks ago. Been jumping in temps, up and down, which has been happening for months it seems. I quit feeding them probably month and a half or 2 months ago. I don't think I've fed since first part of October, so that would be 2 months ago. Whenever the water temps went below 55, I quit feeding, and had been slowing down feeding prior to that, too. And, would they all get swim bladder issue at the same time? That doesn't make sense to me either. I can understand if one got sick and had that issue, but maybe I don't know what causes swim bladder, thus the issue could be the water condition. Checked, PH, Nitrite, Nitrate and Ammonia are all zero and PH is 8.2, so seems all within good numbers. Will watch and see what happens.