Dead koi cause?


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Hello! Because this Forum helped me out last fall with a problem I had (hole in the head or heron strike?) I was hoping someone has seen this before. I had thought all was well when I opened up the pond this spring. Yesterday I found one of my big Koi dead on the bottom of the pond. I fished him out and turned him over to see if I could see what might have been his problem and what a sight! My pond is about 900 gallons and I have had it for at least 20 years now and never had this happen. I currently have 6 Koi and 2 goldfish/koi mutts. None of this showed from the top looking down at him. I hope to get help catching the others in the next few days to see if their bellies are as bad and thought if anyone knew what this was and how to treat it properly to prevent more deaths I sure could use some help. Thank you!
 

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Oh dear....what a sad sight :(. I'm sorry for the loss of your koi.

I understand you've had your pond a long time without problems, but I believe a big part of what killed your koi is related to the small size of your pond for fish as large as koi and the number you have.

I have 4 koi in about 1700 gallons and take a fair amount of precautions for them over the winter. Can you tell us your climate....do you have hard winters? What pond prep you did for winter.......de-icer etc. and have you tested your water?

Try to inspect the bellies of your other koi to make sure they don't have ulcers where you can't see them.

Again I'm so sorry you lost this one :(
 
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Thank you for your kind words, I know from what you and others are saying that my pond size might be an issue now. I got rid of all my goldfish years ago for fear I was over crowded but it might not have been enough. we always run a pump all winter long for oxygen exchange and have a de-icer that we plug in as soon as the ice starts to form. we are in New England where we have been known to get severe winters but the past 5 or so have been milder and last winter we only had a few snow storms.

We do have well water and I do test, it is a bit hard and acidic but not way out of whack and they have always thrived. This was one of my original Koi and I am guessing he had to have been at least 25-30 years old now as I got him when he outgrew a friends pond.

I'd love to build a bigger pond someday, we have the filtration that will handle it....
 
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I really don't have room for a bigger pond, which is why we only have 4 koi, but we've improved filtration over the years. The last few winters I've covered the pond and have been quite impressed, they seem more active over the winter and even some plants remain.

I've seen people use metal panels from tractor and farm supply stores to make hoops over their pond and then cover with heavy plastic. We just make a simple incline with untreated lumber and drape with a pool solar cover. I run air stones and a pond breather under the cover.

Again, so sorry for the loss of your koi......especially such a senior one.
 
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That is very interesting, we have really never thought about covering them for the winter (other than the netting that we have to be sure to use because of the herons). We also have an electric fence to keep the predators away. The combination of the net and electric fence has cured all our issues with any of them. Thank you, we will look into that in the fall.
 
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I was swayed by the science behind the idea. When the pond is covered you greatly reduce evaporation and wind chill.....it also keep the water's surface open which in turn helps oxygenation.

Hope your other koi do not have ulcers. If it were my pond I'be circulating the water and adding oxygen.......our filters are up and running.
 
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I to am in New England and yes we had some good snow so much I had over a foot of ice in my pond. No I am not in caraboo Maine I am in CT. If I am seeing this right it also looks like your koi had a nasty ulcer at his eye. A bloated stomach is usualy a sign they may have had undigested food and gas build up from within. We as humans think if we don't get food or feed three times a day or even eat everyday it's the end of the world. There is no dinner bell in nature . Don't know how they do it but they go 4 and 5 months without any food . They may nibble on some algea but over the winter they just are they don't do to much.

How deep is your pond ?

Did you use a breather?
Air bladder ?
Both ?

The recommended 1000 gallons for the first koi then 500 for each additional koi.

Like you said are winters have been fairly mild recently and your fish have undoubtedly grown they may have reached the critical zone where your pond can't home them safely.

What state are you in?
 
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I to am in New England and yes we had some good snow so much I had over a foot of ice in my pond. No I am not in caraboo Maine I am in CT. If I am seeing this right it also looks like your koi had a nasty ulcer at his eye. A bloated stomach is usualy a sign they may have had undigested food and gas build up from within. We as humans think if we don't get food or feed three times a day or even eat everyday it's the end of the world. There is no dinner bell in nature . Don't know how they do it but they go 4 and 5 months without any food . They may nibble on some algea but over the winter they just are they don't do to much.

How deep is your pond ?

Did you use a breather?
Air bladder ?
Both ?

The recommended 1000 gallons for the first koi then 500 for each additional koi.

Like you said are winters have been fairly mild recently and your fish have undoubtedly grown they may have reached the critical zone where your pond can't home them safely.

What state are you in?
I am in southern NH. I have a huge pollywog filter (the whole filtration system is over kill) with a 1 horse power pump that feeds 2 fairly large waterfalls into the pond 24/7. the deepest point in our pond is about 3.5, maybe 4 feet. I do stop feeding the fish when the water temperature goes to 50 degrees or if they lose interest in feeding in the fall. I do feed the spring/fall mix both spring and fall and I am very careful to feed only what they will eat so there isn't any to rot and decay.
 
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I do think your fish have simply outgrown your pond and sadly, if we don't address it, nature will. 900 gallons is too small for that many koi. I think your oversized filtration has helped up to this point, but you may have reached your limit. It's also concerning that your pond is relatively small in volume but deep - that would indicate that your surface area is small. That can be just as critical as total volume of the pond, especially in the colder months.
 
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I do think your fish have simply outgrown your pond and sadly, if we don't address it, nature will. 900 gallons is too small for that many koi. I think your oversized filtration has helped up to this point, but you may have reached your limit. It's also concerning that your pond is relatively small in volume but deep - that would indicate that your surface area is small. That can be just as critical as total volume of the pond, especially in the colder months.
thank you, I guess I need to build a bigger pond, I might look into having someone dig it out for me this time so I can get a flat bottom. Hubby got tired and just told me that this one "was good enough" and I knew it wasn't at the time. I should have not given in so easily... sigh.
 
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I do think your fish have simply outgrown your pond and sadly, if we don't address it, nature will. 900 gallons is too small for that many koi. I think your oversized filtration has helped up to this point, but you may have reached your limit. It's also concerning that your pond is relatively small in volume but deep - that would indicate that your surface area is small. That can be just as critical as total volume of the pond, especially in the colder months.
it's also critical in warm months, too; there's a direct correlation with surface area and aeration. Ponds/lakes don't need pumps and aerators because there's so much surface area and since most aeration naturally occurs via wind/water mixing, that's why wide ponds do better than narrow ones. In the winter, oxygenation isn't as critical usually because cold water holds much more O2 than warm and the fish are using less at the same time. In the summer though, it's the reverse. So deep is good for keeping cool in the summer while if deep enough (>10'), also creates a thermocline while wide is better for aeration. While most folks think the bubbles rising from their air stones is aerating their pond, it's really not. It's the agitation at the surface, which causes better/more mixing of air and water. So imagine winds and their effect on wide open surfaces!
 
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