hole in ice all winter, 95% of the fish are dead as ice melts

[Lisak1]

We had temps well below -20. We ran the waterfall all winter, as well as an aerator and occasionally turned on the deicer. We have had nearly 70 days of snow cover, which means the pond was also snow covered for all 70 of those days as well. Monday it was 56 degrees and the pond is completely thawed. Today I saw my fish happily swimming around - sweetest thing I've seen in many, many weeks! - even though today the high was 26 degrees. Blah. Tomorrow - new record lows. Anyway, my point is, I have my doubts that the cold is what killed his fish. Having said that, I really have no clue what DID kill them. Very helpful, I know. But sometimes figuring out what it ISN'T is the first step to solving the riddle!

Something just occurred to me as I was re-reading this before hitting post - could it be the snow cover that saved our fish? Snow is a great insulator... maybe our pond was kept warm by all that dang snow!

 

[brokensword]

Maybe get a lab to test the water for toxins of some kind? Or, autopsy a fish or two? This does sound like the winter we had a few years ago here in which the large pond down the road had hundreds of dead fish float up in the spring. It was a very long winter and there was no thaw whatsoever and I'm sure it was the buildup of gasses that did not escape. It seems like that, so I'd be thinking along the same lines. Also, I'm a big believer in user error. Not saying he's negligent, but first thing I always look for is 'what have I done wrong'. Inevitably, I'll find my mistake. Here in Michigan, I only use an aerator and the two times I went out and checked to see if the hole was still open, it was, despite record lows and record snow. Now in saying all that, I have no idea if any of my fish are still alive, but sometime in May probably (j/k) I'll get a chance to find out. The snow is an insulator and should have helped.

Not a lot of help here perhaps, but IF there was a hole open (and even then, I believe ponds can be covered over for a couple of weeks or more and be fine), hard to see how any decaying matter would have hurt the fish. The pond most likely did not get ice as thick as here, so the fish should have been fine at the bottom where the water had to be above freezing. I too don't think it was the cold, and would definitely look for some kind of toxin. Plus, and I'm not sure about this, but would you get accurate readings of water so cold? I think autopsying a fish would tell the tale.

 

[addy1]

His pond is around 30 feet long, he goes down to 6.5 feet, the aerator was in the low end about a foot down. He said he quit feeding when he turned off the pumps, which for him was in early october. He also said he fed the wheat germ food just off and on before he quit feeding.

He told me when we had a brief melt in January early February he saw his fish swimming around nice and healthy looking, then we had a real cold freeze again, this time when it melted , dead fish. All look to be dead long enough to have fuzzyness to them, like mold. Like I said above he had a hole in the ice all winter, never had it totally frozen over. His hole varied in size, the smallest was around a foot.

His water is not real clear, just a little greenish, like single cell algae is starting to grow. He is thinking of paying for a water analysis like you would for drinking water. He tested his water right out of the pond, then let it warm some and tested again. The water tests were perfect.

He is thinking of turning on his filters, but can't decide if he wants to, we are dropping to real cold again next week.

He is beating himself up over this, feels horrible about all the dead fish, it is really bothering him and is afraid to put more fish in. He did not have any koi, just goldfish mix.

I have not turned on any pumps yet, might soon. But with my external pump and diving temps next week I don't want to take a chance with them freezing up.

 

[MitchM]

Any chance an animal could have fallen in the open water and drowned?
That's one concern I have about open water during the winter.

 

[addy1]

He looked did not see anything unless it is hiding in the deeper end. The only problem with that though is his second smaller pond had the same issue, dead fish, open hole all winter, not connected water wise, in any way.

Maybe it was just the winter here, cold, warm, cold, warm, darn right freezing cold, maybe it was too much for the fish. I have no clue in what to tell him to do or even think to do for next winter if he replaces his fish. He is in the shock recovery mode right now.

 

[Sunshine]

Maybe the food was bad?

 

[addy1]

Maybe the food was bad?

If it was the food, it would seem the fish would have died while he was feeding them last fall.

Wish there was a definite answer he sure would be happier to know the problem.

 

[Sunshine]

Did he cut off feeding them well before it got real cold? Did he add any plants before winter? This is a puzzler.

 

[Dave's pond Indiana]

Did he cut off feeding them well before it got real cold? Did he add any plants before winter? This is a puzzler.

She said he stopped feeding in Oct.

 

[mrsclem]

Hate to think it but does he have any problems with anyone in the neighborhood? Vandals have been known to damage ponds and kill fish

 

[MitchM]

If the same thing happened in two unconnected ponds, then I would say the weather was most likely the issue.
I don't suppose he was monitoring his water temperatures by any chance?
My bottom pond temperature has been a rock solid 38F for the whole winter with a solid ice cover.
My ice cover isn't gone yet, so we have yet to see how my fish did though.

 

[j.w]

Can he see clearly all the way to the bottom of his pond cuz what if an animal came for water and fell in and drowned and is rotting under the water? Could that foul the water enough to start a fish kill? Or if the water is cold enough would it preserve any critters that died so no contamination would have happened till the weather warmed up? Would a dead animal float up to the surface or is there a time eventually after floating dead that they sink again and stay down on the bottom?

 

[addy1]

I called and talked to him, no dead animals, no bad neighbors, pretty rural like we are, just a different neighborhood. No plants added, just lilies groomed for the winter.

The two ponds were totally disconnected, i.e. no communication between them.

I am beginning to think it has been the up and down in temps, a longer cold than we have had in years. And once a few fish died under the ice they fouled the water causing more to die. Unable to see the dead until it started melting.
He was not monitoring the bottom temp. I have done that, not this year since we were not here. I did check it today it was around 37-38 with a light ice cover this am..........zero temps lol, wind chill.

I was netting out some leaves that this horrendous wind blew in pulled my net out and it froze solid in a second lol, was so funny. The net was standing straight up when I laid it on the ground.

I am going to tell him about the pond breather I think mitch or someone up north has been using.

 

[brokensword]

addy,

the water would take time to both cool down as well as heat up; I don't think fluctuation of temps--especially with an ice cover, would affect the water temp near the bottom of his pond. And if there was snow coverage, even less so as it would be insulation. Did you suggest he find a place that might analyze his water in more detail and/or do an autopsy? Might also be that a pump leaked toxin into his pond. Or some such similar pond device, if he has any. I've even heard of fish dying when electricity gets to the water.

 

[Sunshine]

Good point on the stray voltage. I once had a pump that was oiled cooled. It sprung a leak and looked like an oil spill in my pond. No fish loss tho.