Koi death


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Hello! I have a question about losing a koi a year, just before spring hits up here in Ohio. For the past few years, I lose one fish, usually one of my older ones
(6-7 years) just when the water is starting to warm. There is not a mark on them. They look perfectly healthy. My pond is 15 foot round, 3 feet deep. We keep the pump going all winter. We are up near Lake Erie in the snow belt. I don't lose any fish during the year, and my pond has been up for over 20 years. We have about 13 koi or goldfish in the pond at various stages of growth. The picture has just been taken....sorry kind of messy. We've had extremely wet weather and cold until this week!
 

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Hello Bunky... (waving to you from the other side of Lake Erie)

My first thought when you mentioned that you leave the pump running all Winter is perhaps "super cooling" the water? I'm not sure if it's a real thing, but I've heard people say that circulating the water at the bottom can make the temps too cold down there for them.

I'm no expert, but I think the idea is that down below the frost line, at the bottom of the pond, you get a bit of geo-thermal heating happening so in the Winter months warmer water I'm guessing is at the bottom. If your pump is circulating everything, I'm wondering if it's getting too cold down there for them?

I've had pretty good success with placing air stones about a foot beneath the surface which doesn't circulate anything too close to the bottom. For good measure I've been using a heater just above the air stones to keep the hole open. I turn off all my pumps for the Winter.

We get our fair share of snow/ice as well so I'm thinking our climates must be similar.

Hope this helps... sorry about losing a fish!

Wammy
 
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Supercooling is not possiblein a pond. I mean, you could potentially lower the water temperature but you won't super cool your pond - which means taking the water below freezing without it freezing. You need pure water to achieve super cooling.

I've heard it said that spring is the hardest time on a pond fish. Their resistance is at it's lowest and they easily succumb to any stressors that might be present in the pond.
 

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could be over chilling of the water or lack of oxygen .So others seem to think the same .You may need a pond heater and turn off the pond and get an aerator
 
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Okay, i'm a bit confused. The pond pump circulates the water out of the pond and through the waterfall, which is on all winter. The temperatures here get extremely cold, sometimes in the single digits, and the top few inches (or more, I've never been able to tell how deep) freezes solid. The waterfall keep the top of the water right under the waterfall, open . I thought that fish go into a sort of
hibernate state during the cold months so how can the water be too cold? If this is true, I understand that they are at their weakest in the spring, but they have been healthy the rest of the year. Thanks for all the responses. Joannie
 
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Your pond isn't any colder than a lake that freezes over in the winter, so the cold water isn't the issue. You say that the pump keeps the water open so oxygen isn't the issue. Since only one older fish dies then the water isn't bad. That seems to point to the fish getting old and the winter is too much for them. It doesn't sound like you can do anything about it. I have lost a few fish and they were always the largest ones in the pond and it was always when I opened the pond in the spring that I found them. Fish die
 
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How soon after ice melt are you finding them? It could be old age, but to loose just one and only at that time, same time each year? That doesn’t strike me as normal, and same goes for any pathogen, parasites, or illness.
 
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My koi are about 15 years old and @callingcolleen1 's are almost 30 years old, my point being, with good care koi are long lived. Colleen overwinters her koi in Canada with great success.

Do you know exactly when the koi die? Could it be while the pond is frozen and you find it after thawing, or is it after the ice has melted?

Since you've said you have solid ice on the surface of your pond and it's usually the oldest koi ( which I'm translating into the largest koi ) it could be a lack of O2. This would probably happen while the pond was still frozen over, with you finding once thawed.

If you're finding the koi after the ice has thawed, it could be a number of things and knowing the parameters of your water testing would help. I've read over the years that Spring is the hardest time on our fish.
 
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Your pond isn't any colder than a lake that freezes over in the winter, so the cold water isn't the issue. You say that the pump keeps the water open so oxygen isn't the issue. Since only one older fish dies then the water isn't bad. That seems to point to the fish getting old and the winter is too much for them. It doesn't sound like you can do anything about it. I have lost a few fish and they were always the largest ones in the pond and it was always when I opened the pond in the spring that I found them. Fish die
That's what makes me feel the worst, it's the ones I have had the longest!
 
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I've had people come over to check my pond, as I wanted to fix my waterfall, etc., and they all said the pond was in excellent shape, water was biologically right, etc. I have healthy fish which spawn, the water is semi clear, so I'm assuming that the fish I find are either passing during the winter, and I only see them in the early spring thaw; yes, they seem to be the oldest (largest) ones. I guess there really isn't much I can do, but I appreciate all the responses. Every fish seems great now, and they're starting to eat, so no problems presently. Thanks again. Joannie
 

callingcolleen1

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Hello! Sorry to hear your mature fish died. (7 year old koi are not anywhere near old as koi usually out live their owner if conditions are good)
If your pond is only 3 feet deep and you do not use a heater, then you will not have three feet of water over winter as the ice displaces the water as it turns to ice. it is most possible that the fish were over crowded as the ice thickened and the water below the ice becomes less deep. On a very cold winter you won't have much water left under the ice. Then the bigger more mature fish will suffer as they are larger and need more oxygen than the smaller fish.

I would say that pond is too small and not deep enough to house larger koi over very cold winters. You will need to make the pond deeper and larger as the koi grow, so ensure they have enough room over the winter or thin out the larger koi and give to a good home and just keep smaller fish over winter.

I have in the past kept my biggest koi in only three feet of water, but in my upper ponds where the water is at a consistent three foot level all the time. My upper ponds are always at the same water level all the time. The ice grows above in the upper ponds, as the water is pumped from the bottom pond to the upper ponds, and flow to a maximum level. Then excess water drops down the water way to the next lower level pond, until it reaches back down to the bottom pond. I also use one heater for all four of my larger connecting ponds to keep the ice down in the past.

I now have a much larger 5 foot deep top pond (8 by 8 feet wide) to house the largest koi and that pond is connected to the three other lower level ponds and they all flow together at all times. You could also take apart that waterfall and turn it into a deeper pool of water that flows back down to your shallow 3 foot pond and have the largest koi in the upper deeper pond. Over the years I had to enlarge my ponds as the koi grew to ensure the biggest koi would have a clean deep pool of water to rest over the long cold winters that we have here in Canada. Even though I use only one heater for all four connecting ponds, my pond water is still very ice cold all winter, registering at just barely above freezing. Water in our ponds cannot be super chilled so that is not a issue. I now use cattle panel cold frames to keep the ice down as now that my ponds are larger the one heater struggled to keep the ice down. With the cattle panel cold frames over top the one heater can now keep all ice almost all away over winter. Good thing too cause this past winter was so extra long and cold, with weeks of extreme cold, reaching -40 below zero this year.
 
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