Fish dying as water is turning colder


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Hello,
I have an 8000 gallon pond that I’ve had for 2 years and we just now started to get into the cold weather which turned extremely fast. My fish seem like they are stressed some are laying on sides and I’ve already lost a large Butterfly Koi and several smaller
Comets. I’ve tested on my water parameters ammonia , nitrate, nitrite, copper, and phosphate are all zero. My pH is 7.6, my KH is 50 to 100 parts per million, and my GH is 100 to 200 parts per million. My local Aquarius told me to add some pond Salt slowly a little bit each day. Can you think of anything else that might be happening?
 
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addy1

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Welcome to our group!

How many fish are in the pond? Do you have any water movement going on right now?
 
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Welcome to the GPF!

I don't know why someone would recommend salt without first knowing what's going on. And in an 8000 gallon pond you'd need A LOT of salt to make a difference. Salt can be helpful for treating skin infections or parasites in fish, but the best way to deal with it is by giving the fish a salt bath in a separate container. Adding salt to your pond is something that most are rethinking, as it can create parasites that are immune to salt. It's also hard on your pond plants, if you have them.

More information would be helpful - are you sure on the size of your pond? 8000 gallons is a sizable pond. How many fish total and what size/age? What kind of filtration? Did you recently change anything - add new fish for example? Do the fish show any signs of trouble other than their behavior - red markings on gills or fins for example? Bloating? Eyes cloudy? Did you add anything to the pond? Any possibility that the pond was contaminated with pesticides or weed killer? Did you recently shut down the pond and turn off filtration?

Cold water won't kill koi or comets - they're hardy fish, so you can cross that off your list of possibilities.

Anything you can share about the situation will be helpful!
 
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Sorry to hear you are losing fish.

Salt is not a good idea for cold water. It actually lowers the point at which water will freeze so the pond will not ice over until it's below normal freezing temperatures. That ice layer can actually insulate the water beneath it, so using salt would be counterproductive.

Some fish are more susceptible to cold than others, but most do fine in winter with a hole in the ice and enough aeration. Something else must be going on for you to lose so many fish so quickly.

What is your pond's ammonia level and what type of tests are you using? The strips are very inaccurate and pretty useless. The liquid test kits are much better.
 

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@12cats Sorry for you and your fish. Could anything have leaked into the pond or from the air? What do the deceased fish look like after death? Can you see anything out of the ordinary on the fish that are alive? I really am not familiar w/diseases but I think that the people who are here might need to see close up photo's of the fish that might show them something.
 
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Thank you all for responding. I will try to answer everybody's questions. I built upon myself 2 years ago and had to have it filled with a water transport system so I know how many gallons it took to fill it. It took 8000 gallons. The pond is roughly 21 wide by 34 long and six foot deep in the middle, with different layers of shelving going around all sides. I have a large aerator running Oh, and a small pump should I keep in my skimmer so it doesn't freeze. The pond store that recommended the salt said it would help with their Gill function. I use the API liquid water tester kit. All parameters were zero, KH was 50 to 100 PPM, and GH was 100 to 200 PPM. There was no chance of pesticides or anything getting into the pond from runoff. I am not sure of the exact number of fish because there were a lot of babies born this spring and I haven't been able to count them all yet. Prior to the baby's I had three large koi about 16 in each, one large golden orf about 20 in long and probably about 15 ...4 to 7 in goldfish and 4 6 inch golden orf's. All of these fish with the exception of the orfs I bought from a man who was closing his pond down. I have had them since March with out any losses. His pond was much smaller and not very deep. And he lived where the winters get much colder than in my part of Ohio. I have lost a large butterfly koi. And 4 or 5 goldfish. I was able to get another one of the large koi who was laying on the bottom out with a large net and he is in a container in my garage. It is still just lying on his side although he seems to be a little more active since the water is warming up. he does have red spots all over him but I don't know if that's from him lying on the rocks been trying to scoot around or what. the temperature dropped here from like 45 to 18 degrees overnight. Now the temperatures are back in the 40s and 50s.
 
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I forgot to mention the large Butterfly Koi that died did not have any kind of marks or signs that anything was wrong with it.
 

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It is a mystery to me. If it was an oxygen problem then the big fish would be dying I would think before the smaller goldfish. I did read online that red spots or sores can be a sign of a bacterial infection. But that usually happens if water quality is not good but you say your water tests are fine. Wish someone would sign in here that really knows about this kind of stuff. Whenever I have a goldfish die in my pond which is hardly ever,usually happens at the start of Spring, I usually do a partial water change. Don't really know if this helps much but after I do it no fish die. In Summer I do partial water changes all season just cuz I don't think my filtering set up is that great. I have well water so no need to add dechlor to it. I have been doing these partial water changes for 15 plus yrs. I never do it during the cold months tho. Wonder if your fish could have some sort of parasites inside of them? Just grasping here as have no answers for you. Wish I did.
 
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I think your KH could be low. Is your PH stable, have you tested both morning and evening ?
 
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No I only tested the ph when I did the other testing which was in the morning.
 
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pictures please, fish laying on their sides are fish not doing well at all
 
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It's hard to get a clear picture because of the depth, but the ones that are not acting right are just laying on their sides. If you try to get them with a net, they do move away but go back in the same position. The ones that seem to be ok are either just sitting on the bottom or seem to be suspended in the water. It warmed up the last two days and most are moving slowly around the pond. The koi I had out in the garage didn't make it. I did not think it would and I didn't want it dying in the pond and maybe I couldn't reach it to get it out. The picture is of the one that just died.
 

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i would catch them all that are laying on there sides and get them to a hospital tank in your home the cold puts them into a type of hibernation. they are literally inches from death in the winter months but thats what they do . Get them warmed up and into a controlled hospital tank with lots of air and i would also add start right or any similar product from your local fish store bring one of the fish to a good store and have them test for parasites and your water take it step by step . Usually when they start laying on there sides it's bad news and you don't have long to fix the problem
 

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Agree with @Lisak1 and others — salt isn’t the answer....and we need more information about your pond.

I haven’t read carefully through all of the replies, so I hope I’m not asking what’s already been addressed. But, where do you live, how deep is your pond, how many (total) fish do you have, including their approximate sizes?
 
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they are literally inches from death in the winter months
I'm not sure I would agree with that assessment. They do slow down dramatically though so fish moving very slowly or even staying perfectly still at the bottom is normal and not concerning. Laying on their side is another story though and is definitely not a good sign.
 
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With a pond that size, I would think there would be very little change in the temperature of the water, even with that big a swing in air temp. What is your current water temperature?

I, too, am suspicious of your KH, that it is too low. I keep mine around 200ppm. My filters work best at that level. KH is easily raised with plain old baking soda. You can get large bags at big box stores like Costco for a good price.

A higher KH will keep your pH stable. It can raise your pH to around 8.2 or so, but that is no problem. Keeping it stable is the important part, and if it is bouncing around, it will stress the fish. If it isn't addressed the pH can crash, making the water acid and killing the fish and your beneficial bacteria.

I do know of some people that have to bring their koi inside for winter, as some of their fish just can't tolerate the cold water. I really don't think that is the issue here, especially with that amount of water. Others cover their pond with a greenhouse type structure to keep it from freezing. We do that and the water temperature never drops below 45 degrees, even with single digits and feet of snow outside. It keeps the wind off the pond, which creates evaporation that cools the water, and it holds in the warmth from the water and the ground. It works amazingly well.

For now I would address the KH and bring that up. You will need to periodically dose it since it gets used up with the nitrogen cycle, so it needs to be tested once in a while.
 
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Agree with @Lisak1 and others — salt isn’t the answer....and we need more information about your pond.

I haven’t read carefully through all of the replies, so I hope I’m not asking what’s already been addressed. But, where do you live, how deep is your pond, how many (total) fish do you have, including their approximate sizes?
Yes in a previous reply I answered your questions. Would it hurt to put in melafix as a precaution?
 
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Melafix does nothing. There was a recent study proving that and I will see if I can find that. Also, since it's an oil, it doesn't mix well with the water and it can actually coat the gills of the fish and make it more difficult for them to breathe. The last thing you want with an already compromised fish is to stress them more with something you put in the water.

Always fix the water first and you water is low on KH. Correct that before you add any kind of "medication" to the water.
 
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With a pond that size, I would think there would be very little change in the temperature of the water, even with that big a swing in air temp. What is your current water temperature?

I, too, am suspicious of your KH, that it is too low. I keep mine around 200ppm. My filters work best at that level. KH is easily raised with plain old baking soda. You can get large bags at big box stores like Costco for a good price.

A higher KH will keep your pH stable. It can raise your pH to around 8.2 or so, but that is no problem. Keeping it stable is the important part, and if it is bouncing around, it will stress the fish. If it isn't addressed the pH can crash, making the water acid and killing the fish and your beneficial bacteria.

I do know of some people that have to bring their koi inside for winter, as some of their fish just can't tolerate the cold water. I really don't think that is the issue here, especially with that amount of water. Others cover their pond with a greenhouse type structure to keep it from freezing. We do that and the water temperature never drops below 45 degrees, even with single digits and feet of snow outside. It keeps the wind off the pond, which creates evaporation that cools the water, and it holds in the warmth from the water and the ground. It works amazingly well.

For now I would address the KH and bring that up. You will need to periodically dose it since it gets used up with the nitrogen cycle, so it needs to be tested once in a while.
I have ordered some baking soda and have already put on a solar cover. A cheap one but I'm hoping it helps. Water temp last night was. 43, it has been in the mid fortys for a few days. It seems like the warm up helped. It is impossible for me to get to the fish and it looks like most of the ones that were lying on their sides have died. Would it hurt to put melafix in as a precaution?
 
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Melafix does nothing. There was a recent study proving that and I will see if I can find that. Also, since it's an oil, it doesn't mix well with the water and it can actually coat the gills of the fish and make it more difficult for them to breathe. The last thing you want with an already compromised fish is to stress them more with something you put in the water.

Always fix the water first and you water is low on KH. Correct that before you add any kind of "medication" to the water.
Thanks for your advice.The baking soda should be here tomorrow.
 

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