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Pond Goldfish Inexorably Dying

Guest drbob

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Guest drbob

Over the past 15 years my 600 gallon (7'X7') outdoor goldfish pond has had only an occasional loss of goldfish. Starting three months ago perhaps one fish a week seems to suddenly die. There is no prolonged illness and no visible external ulcerations, inflammation, fungal-like growths etc. The doomed fish will appear to be feeding and swimming normally and a day or two later it's belly up. After 4 or 5 fish died I purchased 7 new ones a month ago(small to medium sized). Subsequently, 4 more of the original fish have died (including two I've had for 15 years) but none of the new ones (so far). Size does not seem to be a factor as fish affected are large or small (a couple left over from last year's spawning).

Initially I empirically treated with antibiotic fish food and then did water changes and added beneficial bacteria for my biofilter. All to no avail. the remaining fish, the seven new ones and two large originals, are quite active and feeding briskly though I suspect another will be belly up soon.

I might mention I "autopsied" two fish and didn't see anything particularly unusual.

Any thoughts why this would be happening in such an intermittent but relentless manner and (apparently) not involving the "new" fish? Any other "global" remedies?



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  • Regular Member

Hello Drbob and welcome to Kokos.

Just a couple of questions for you, if you don't mind.

1. Does the death of a fish follow a period of heavy rainfall? Have any neighbours been spraying herbicides, pesticides?

2. Is your pond accessible to foul play, ie. something thrown over the fence?

3. Did you do anything different over winter this year? it appears the deaths started with the warmer weather.

4. Any new plants in the vicinity that may drop leaves, flowers, etc into the pond?

Really it is a mystery. If there are no apparent external contaminents or likely causes for these deaths the next step is to examine the ecosystem of the pond itself.

1. Any new plants or renovations to the pond?

If you could answer as many questions as possible from the questionaire at the top of the page we will be able to build a picture of what is happening inside pond and might find some clues there.

edit: the white box questionaire does not appear to be at the top of this page. If you click 'back' and return to the Diagnosis/Discussion forum it should be there.

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Guest yabbie

Toxins in the pond liner? Heavy metal build up in the tissues? Breaking down of the pondliner? They weren't as careful with pond liners 15 years ago. :unsure:

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