Solving the Mystery of Dying Carp in a Natural Pond: Help Needed

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In summary, the grass carp in the pond are dying off, while the other fish are completely fine. The area we live in was used for coal mining in the 30's up to the 60's, so Brett thinks the pH might be at least slightly acidic. There's still plenty of water in the pond, so the food may still be there. Brett is going to check the pH and see if it's low. If it is, he'll move the carp to cleaner water. If they seem to do better, that's good evidence that the problem is environmental. But if they continue to do poorly, then maybe it's disease.
  • #1
My problem is that the grass Carp in our pond seem to be dying off for some reason, while the other fish are completely fine. The area we live in use to be used for coal mining in the 30's up to the 60's, so I always figured the pH was at least slightly acidic. You can actually walk out into the back yard and easily find concentrations of brittle coal pieces scattered here and there. It's pretty much a natural pond that maintains it's own amount of water and is fairly shallow with a max depth of ~3-1/2' at most... 80% of is only ~1 to 2' in depth. The overall size is a little under one acre, possibly 3/4 of an acre. No filtration system.

We stocked the pond about two or three years ago and everything has been fine, up till now. They should have a life expectancy of ~7-8 years so something is definitely happening. There's still plenty of water grass in the pond, so the food it still there. The fish look completely fine with no external abnormalities or anything else out of the ordinary. They're just hitting a point where every day or so a new one will pop up just floating on the surface upside down. They're still alive, just extremely lethargic... that's what made me suspect the pH, but I figured the rest of the fish would be affected too.

I just picked up some pH strips and about to check the level. If anyone has any ideas or recommendations, they would be greatly appreciated!

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  • #2
I'd say disease maybe.
  • #3
Disease is a possibility, but low dissolved oxygen levels might have something to do with it. If you have enough oxygen-consuming biomass in that pond your fish may be suffocating. Lots of little garden/backyard ponds have fountains in them to supply aeration for just that reason.
  • #4
If the oxygen is low most fish will swim just below the water surface.
  • #5
Yes, Borek is right, you will actually see them{wide mouth} gasping for air right below the surface.
  • #6
Well, I just checked the pH. On a scale from 1 to 14 (1 being acidic) it's at about 5-1/2 or 6. That seems ok.

There's a decent amount of biomass in the pond, but it doesn't look as though it would be too much. If I had to guess i'd say about 20-25% of the ponds subsurface area has grass and other plants growing. The fish also don't seem to be gasping for air... they're actually breathing very, very slowly. At first they look dead, but when you get up close, you can just barely tell that they're breathing.

With what everyone's said so far, it's probably disease. The oxygen level is probably ok since you couldn't even tell if there were carp in the pond until you see them floating upside down all of the sudden. I find it strange that it's attacking just the Carp and not the Bass or Bream.

Moonbear suggested taking one to an ichthyologist. I might have to do that since I can't afford to restock the pond. I just hope there's some form of treatment that's viable because i'd hate to have all my Carp die, and run the rick of it happening again if I restocked it... that and the possibility of the grass and cattails getting out of control.

Thanks for the input guys!
  • #7
Perhaps move each carp to cleaner water. Perhaps it's a particular virus or bacterium or parasite or . . . .
  • #8
I'd catch some and move them to a fish tank. Be sure to feed them and aerate the water.

If they seem to do better, that's good evidence that the problem is environmental.

But if they continue to do poorly, then maybe it's disease.
  • #9
That's not a bad idea. The only problem is that the ones that are dying are pretty large... about 1-1/2' to 2' in length. I walked outside this morning and saw yet another one floating.

I called a local fish store and they said the only thing viable would be to send a water sample to a local lab. I happened to find two old film containers and got a couple of water samples from different spots... just hope the lab doesn't charge an arm and a leg.:frown:
  • #10
So, how do we fix it if the oxygen is the problem?

I am having the same problem with my fish. I have large colorful goldfish. They have always been healthy and playful, now I have one that is staying on top gasping for air it seems. So, should I take out some of the plantlife I have in there? Is that what it means, that the plants are taking the oxygen from the fish? I have a small pond and only have 2 small plants, a lillypad and 3 little leafy things that float around the water(doesn't seem like much to me). I can try to take a pic and post it if that helps, but are you saying that when a fish is alive, but floating at the top gasping or at least, that is what it looks like, his mouth is moving in and out as if he is eating, but he really isn't moving much, that he needs more oxygen?

Thank you so much for your help. I am so glad I found this site!

  • #11
Oh yea, so if I take out some of the plants now, am I too late or will it put oxygen in the pond right away and perhaps this fish will make it? What about the other fish, will it mess them up if I take away some of the plant life, will that be too drastic of a change for them?

Thank you!
  • #12
sillymom, do you have an aerator in your pond? You may need to either add one, or increase the aeration rate. And, as someone suggested above, check the pH, as that can affect how much of the oxygen in the water is available.

Something else that just came to mind is all the rain some areas are having recently. Perhaps the runoff from a lot of rain has disrupted the pond environment.
  • #13
How hot is it outside? Hot water holds less oxygen than cold water does and increased temperature in water increases metabolism in fish. Is the pond shaded? If its not, partially shading it will increase the circulation in the pond because cooler water will sink. Therefore you might not need to aerate it.
  • #14
how much did the lab charge
  • #15
I think water temperature is one possibility. If the water gets too warm, in addition to reducing oxygen, it could enhance parasites or diseases, or perhaps there could be anaerobic bacteria or other micro-organisms growing. This is just speculation.

This might be of interest - Spring Viremia of Carp
Spring viremia of carp (SVC) is a viral disease that can cause significant mortality of common carp (Cyprinus carpio).

In natural outbreaks, mortalities were confirmed in spring of 1969 and 1970 in Yugoslavia when water temperatures ranged from 12°C to 22°C (54°F to 72°F).The optimum temperature for viral replication in vitro is 20-22°C (68-72°F), . . . .

USDA on Viremia - [Broken]
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  • #16
DeanBH said:
how much did the lab charge

They charged $75, which is MUCH less than what I was expecting. Results should be back by this coming Tuesday. The receptionist said they'd normally have it done faster, but mentioned something about a big project going on. (I bet they all really just went to Bonnaroo '08:rofl:)
  • #17
Water plants

Please don't pull up your plants. They take up carbon dioxide from the water and turn it into oxygen. So if anything, the plants are helping to aerate your pond. My best guess for the various problems mentioned on this page would be temperature and low dissolve oxygen or potentially some sort of parasite. Gill parasites are very common, especially in warmer months.
  • #18
A little late coming in on this.

I agree with Astronuc as far as moving to clean water when fish show signs of distress. A friend has large fish and keeps a tough (food/water grade) handy in case he needs to move them. In a pinch he's also used a Sterlite clear plastic storage container. I'm not sure this would be good for a long period of time, though. They're easy to store when not in use and come with a lid for transport. When all else fails he's also used the bathtub.

Some fish are also more sensitive to chemicals so I'd wonder about their food source or other contamination if you haven't found the cause yet.

I hope you've solved the mystery and all is well.

Far Star
  • #19
I completely forgot about this thread till Ed Aboud PM'ed me, but unfortunately the lad couldn't find anything out of the ordinary except for higher levels of acidity... which was expected. The lab only suggested that may have been a type of virus.

Thankfully, the number of Carp that have been dying seems to have stopped since I haven't seen a new 'floater' in a five days or so now. Hopefully whatever was causing it has stopped completely.
  • #20
Grass Carp only eat plant materal, they are suppose to be sterile also. The nature is that you put the in your pond if you have a problem with water plants and algae. when the food supply goes down the fish die. If you still have a lot of plants you might want to contact your county extention agent.

1. What could be causing the carp to die in the natural pond?

There are several potential factors that could be causing the carp to die in the natural pond. These include water quality issues, disease outbreaks, lack of oxygen, and predation by other animals.

2. How can we determine the cause of death for the carp?

In order to determine the cause of death for the carp, it will be important to conduct a thorough investigation of the pond. This may involve testing the water for pollutants, examining the fish for signs of disease, and observing the behavior of other animals in the pond.

3. What steps can be taken to prevent further carp deaths?

If the cause of the carp deaths is identified, steps can be taken to address the specific issue. For example, if the water quality is poor, steps can be taken to improve the water circulation and remove pollutants. If a disease outbreak is the cause, proper treatment and prevention measures can be implemented.

4. Is there a possibility of human intervention causing the carp deaths?

While it is possible that human activities such as pollution or overfeeding could contribute to the carp deaths, it is important to thoroughly investigate all potential causes before making any conclusions.

5. How long will it take to solve the mystery of the dying carp?

The amount of time it takes to solve the mystery of the dying carp will depend on several factors, including the complexity of the issue and the availability of resources for investigation. It is important to be patient and thorough in order to find the true underlying cause of the carp deaths.

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