Bought new fish, now old fish dying.


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Hello all,
We have a 1200-1500 gallon pond. It is well aerated with a smaller uphill pond and waterfall. The water is supplemented by a pump we have in the lake we are on. Until a couple weeks ago, all the goldfish remaining in the pond were "born" there. Since we've lost so many fish to predators, we decided to diversify the gene pool, and bought 10 new Shubunkins and red and whites from a reputable store. When our goldfish started dying a few days ago, we attributed it to the heat wave, but now the count of dead dish has risen to 13, and none of them were the new fish. Incidentally, we've seen no gasping at the surface or other abnormal behavior. What do you think?
 
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I would rule out the water and wouldn't bother testing it, If the water was somehow bad then the new fish would die. The same with quarantining the new fish. If there was one sick fish then the new ones would be dying too. I have no idea why some are dying but it could be that the old ones are the sick ones and they will eventually kill off the new ones or it could be maybe there is something in the water like fertilizer. I doubt that you will ever know. If it continues to happen I would drain the pond and refill it but I wouldn't automatically reach for some snake oil to fix a perceived problem.
 
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So I do need to note that one of the new red and whites has some kind of sore on its side, but none of the others have developed anything like that. All our losses in the past have been due to predators or winter asphyxiation. Until the other day, I'd never found any fish dead in the pond in the summer.
 
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The sore could just be a confounding and spurious variable that will lead you to try to fix something that isn't the problem. I would take that fish out no matter what and take him back to the store. No one likes to see their fish die but you have to weigh the cost of trying everything under the sun to buying new fish. So far your new ones are doing fine If that changes then as I suggested drain the pond and refill it. You have lake water so the cost should be 0. You could also run a test and put your goldfish in a wading pond and see is any more die. If so then it's time to get rid of all the old stock.
 
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I would lean toward you introduced something into the pond with the addition of the new fish. If you can't see any signs of anything wrong with the fish, they could be succumbing to an internal parasite.
 
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I would lean toward you introduced something into the pond with the addition of the new fish. If you can't see any signs of anything wrong with the fish, they could be succumbing to an internal parasite.
could it be that the new fish had developed an immunity o whatever it is that's killing the old fish?
 
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My opinion is your old pod was a "closed system" for a long time. When you brought in new fish, your old fish were exposed to something they didn't have immunity against , so they perished. Parasites are always present in the water and most of the time healthy fish aren't affected, but if it's something they'd never been exposed to they may get sick and die.

With the appearance of an ulcer on the side of one of your new fish, I think you have your answer. An ulcer is always a sign of infection....it could be a secondary infection or an infection from a parasite.
 
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Without a doubt the addition of new fish caused the deaths of your other fish.

This is why we encourage a quarantine period of 4-6 weeks prior to adding to your established pond. Fish in quarantine will often times show signs of illness even if it wasn't present ( or noticed) when the fish were first purchased. If they are sick or have parasites they can be treated much easier in a smaller more controlled environment (quarantine/hospital tank)
 
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Quarantining is one of those things that sounds good but IMHO is usually unnecessary when adding new fish. I'm open to being convinced but the way I look at it, the new fish come from a tank of many fish and have been in the tank for a long time. If they were sick the pond store would have taken them out before they killed the rest of their fish.
 
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You said your pond is supplemented by water from a nearby lake..... there is a chance that a parasite or some kind of contaminates might have come from there..... you could stop that water flow and see if that helps
 
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I guess using the term "sick" is confusing. All fish carry parasites, healthy fish won't become ill with low levels of them. When the fish get stressed (just bagging and moving fish to a new environment can cause stress) it can give the parasites a chance to then take hold and sicken the fish. The thing that happens when adding new fish is that you are possibly adding a parasite that the current fish do not have immunity to. That's why many times when new fish are added it's only the fish you've had all along that end up dying ( sometimes but not always the new fish die too) Many goldfish and koi keepers will quarantine and treat with a broad spectrum antiparasitic medication before ever adding new fish to the current collection. Some will even use a microscope to confirm exactly what parasites the new fish may be carrying. That way they can be sure to treat with the needed medication.

And just an FYI about where you buy fish. I worked in a big chain pet store. The aquatic system was treated with salt and other antiparasitic medications (when deemed it was needed). The only fish that were removed from the system were the ones that had bacterial infections and needed antibiotics. New fish were added weekly and all fish except feeder tanks were on the same filtration system. We had fish dying daily (as is expected when adding new fish without quarantine) employees net out dead fish throughout the day so customers don't see them.
 
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Very distressing for you with so many losses. Really sorry to read about it.
So basically I think the new fish are coincidental to the death of the original ones! Why? Well the new fish are not dying and if they had something that killed the original ones then they would be suffering as well. So I am assuming the deaths were going to happen anyway. So now keep a close eye on the healthy new ones for any sign that they are getting whatever the original ones had. It could be an environmental problem that eventually caught up with the original ones. No treatment at this stage as you dont know what you are treating. A close eye on the new ones is what is needed now. Are any of the original ones still alive. Some photos of the fish and pond might help us help you.

Ray
 
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New fish have built up immunity to what ever they carried in with them.

Believe what you will but adding new fish without quarantine is not a good idea for this very reason. After water quality issues it's probably the second cause of fish illness and loss.

When you've kept several fish for many years you learn these things. And some of us learn them the hard way :(
 
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New fish have built up immunity to what ever they carried in with them.

Believe what you will but adding new fish without quarantine is not a good idea for this very reason. After water quality issues it's probably the second cause of fish illness and loss.

When you've kept several fish for many years you learn these things. And some of us learn them the hard way :(
I think quarantining is a very good idea but in this case if the new fish have a "killer disease" that kills other fish in a couple of days but they are immune to it then the quarantine would only have delayed the inevitable. the immune new fish would have presumably still be deadly when released from quarantine. Anyway as the OP did not do that then I suggest a close watch on the new ones now they are in the pond. By the way I don't know of any disease that a fish could have that would kill all the other fish in a pond in a couple of days but not kill themselves! What disease are you thinking of? Parasites don't act that quickly.
 
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Also, I've had new goldfish in quarantine look completely healthy. Then after a week or so they have visible ick spots. This is the reason for quarantine. Hopefully you will recognize the signs of illness/parasites and treat the fish while in quarantine.

I also added a new goldfish (who by the way looked healthy to me) to an aquarium without quarantine and killed all of my favorite goldfish fish (this was years ago) and this experience was a hard lesson learned for me. I will never add fish without quarantine and I would never recommend it.
 
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Also, I've had new goldfish in quarantine look completely healthy. Then after a week or so they have visible ick spots. This is the reason for quarantine. Hopefully you will recognize the signs of illness/parasites and treat the fish while in quarantine.

I also added a new goldfish (who by the way looked healthy to me) to an aquarium without quarantine and killed all of my favorite goldfish fish (this was years ago) and this experience was a hard lesson learned for me. I will never add fish without quarantine and I would never recommend it.
Agreed with everything you said but in the OP case the new fish are healthy (as far as she can tell) and the existing ones all died from something (not sure about "all"). This is a strange case I guess that is my only point to the OP. Keep an eye on the new fish.
 
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