Fish starting to die


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Help! I have had my pond for 13 or14 years and have not had issues like this in the past. The pond is 35 foot long, 25 wide and 2 foot deep. There is a 3 foot wide shelf that is only a foot deep and boulders on the shelf so i am guessing the volume in in the 7,000 to 8,000 gallon range. The last couple of weeks, i am finding one or two fish that have died every day. I have one koi and maybe 50 or so gold fish so am not thinking it is overstocked for it's size. Bought a new API test kit and the ammonia, nitrite and phosphate are all at zero. PH looks to be about 8, which is high. Would this be enough to cause fish to die? Those that i have lost are anywhere from 2 inch to 6 inch. It is really disheartening to keep seeing fish dying.
 
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A Ph of 8 would not hurt your fish at all unless it changed by a very large degree all of a sudden. The tap water for my city runs 8.1-8.4 according to the city water report, my pond has a natural diurnal swing from about 7.9-8.2 every day and my fish are thriving.

Have you added any new water to your pond recently, or have heavy rains caused any runoff into your pond? The test kits can't test for pesticides and such that can wash into water.

Have you recently introduced any new fish or plants to your pond, or has new wildlife been visiting your pond?

Have you conducted any autopsies or taken any of your ill or dying fish to a fish veterinarian if you can't find anything via your own examinations? At minimum, with a dead fish even if you feel you are too squeamish to check internally, if the fish isn't decomposed but is newly dead you'll want to do a full external check for parasites, sores or other damage to scales or fins, lift the operculum (gill cover) to look at the gills for signs of parasite, disease or damage, and check the eyes and mouth.

I'm relatively new to ponding, though not to fish, so hopefully someone else has some ideas or thoughts I don't know about.

Good luck figuring this out, I'm sorry about all the fish you've been losing.
 
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A Ph of 8 would not hurt your fish at all unless it changed by a very large degree all of a sudden. The tap water for my city runs 8.1-8.4 according to the city water report, my pond has a natural diurnal swing from about 7.9-8.2 every day and my fish are thriving.

Have you added any new water to your pond recently, or have heavy rains caused any runoff into your pond? The test kits can't test for pesticides and such that can wash into water.

Have you recently introduced any new fish or plants to your pond, or has new wildlife been visiting your pond?

Have you conducted any autopsies or taken any of your ill or dying fish to a fish veterinarian if you can't find anything via your own examinations? At minimum, with a dead fish even if you feel you are too squeamish to check internally, if the fish isn't decomposed but is newly dead you'll want to do a full external check for parasites, sores or other damage to scales or fins, lift the operculum (gill cover) to look at the gills for signs of parasite, disease or damage, and check the eyes and mouth.

I'm relatively new to ponding, though not to fish, so hopefully someone else has some ideas or thoughts I don't know about.

Good luck figuring this out, I'm sorry about all the fish you've been losing.
I really can't tell you if there was a large swing in PH or not, I haven't tested the water in years as when i did test then, the water tested fine. It has been long enough ago that i don't remember the PH numbers then. I have added water as it has been hot and windy with little rain so evaporation was an issue. My well water PH tests at about 7.5. I haven't added any new fish or plants in a couple of years, i am usually pulling plants and tossing in the compost bin. We did have have a couple of big storms in the last couple weeks but the grass isn't treated with anything so nothing to run off into the pond. Looking externally at the fish look ok to my untrained eye, eyes clear, gills look ok , there aren't red not spots or sores on them. What would i look for internally?
 
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I really can't tell you if there was a large swing in PH or not, I haven't tested the water in years as when i did test then, the water tested fine. It has been long enough ago that i don't remember the PH numbers then. I have added water as it has been hot and windy with little rain so evaporation was an issue. My well water PH tests at about 7.5. I haven't added any new fish or plants in a couple of years, i am usually pulling plants and tossing in the compost bin. We did have have a couple of big storms in the last couple weeks but the grass isn't treated with anything so nothing to run off into the pond. Looking externally at the fish look ok to my untrained eye, eyes clear, gills look ok , there aren't red not spots or sores on them. What would i look for internally?


I've done full autopsies on my fish before, and sometimes it's very obvious what the problem was (eg, large parasitic worms, large cysts, bowel obstruction) and other times you cannot tell at all (or it's an ambiguous sign, like an enlarged liver) and you would need to take a sample and look under a high powered microscope. Try to find some good clear anatomy guides before you start (both illustrated and photos of real autopsies of fish), and just know it's really not easy to tell with your very first couple of fish dissections for that species what is normal and what isn't.

Hopefully someone else has some better ideas!
 
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We had a large die off one year that we believe was caused by ducks in the pond introducing a parasite. No real evidence of that, but the water tested fine and, like your fish, they had no signs of anything externally wrong. They were dying off one or two a day for several weeks, so the assumption was that the parasites were moving from fish to fish, infecting one or two at a time. They all exhibited the exact same symptoms before they died, but it happened very quickly. As soon as we realized they were showing the signs, they were gone within hours. We finally treated the pond with Prazi and within two days the fish stopped dying. Didn't lose a single fish after that point. So whatever it was the Prazi stopped it.

I wish I had felt equipped to do a fish autopsy - it would have been interesting to see if there were internal parasites of some kind. That year when the ducks showed up we were so excited to see them. We'll never allow them to stay again. Guilt by association!
 
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Could the issue be O2? Do you have enough aeration....water hold less O2 in hot weather. Very sorry to hear of your losses.
 
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Could the issue be O2? Do you have enough aeration....water hold less O2 in hot weather. Very sorry to hear of your losses.
I have six 2 inch air stones. There is also a 25 foot stream with two small falls and the large water fall so water is moving. I don't have a way of measuring the O2 level.
 
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We had a large die off one year that we believe was caused by ducks in the pond introducing a parasite. No real evidence of that, but the water tested fine and, like your fish, they had no signs of anything externally wrong. They were dying off one or two a day for several weeks, so the assumption was that the parasites were moving from fish to fish, infecting one or two at a time. They all exhibited the exact same symptoms before they died, but it happened very quickly. As soon as we realized they were showing the signs, they were gone within hours. We finally treated the pond with Prazi and within two days the fish stopped dying. Didn't lose a single fish after that point. So whatever it was the Prazi stopped it.

I wish I had felt equipped to do a fish autopsy - it would have been interesting to see if there were internal parasites of some kind. That year when the ducks showed up we were so excited to see them. We'll never allow them to stay again. Guilt by association!
I have had ducks visiting since the pond was built so not sure it is them but it could be. The ducks had also gone into my little preformed before my son and I built the 'lake' in the back yard. Is the Prazi a liquid or powder and where do you get it? I wouldn't mind trying this as i don't want all of them to die. They all have looked fine to my untrained eye, just were dead.
 

Jhn

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Praziquantel used to treat intestinal worms , flukes, etc. it comes both ways liquid or powder. Prazipro is the brand name many use.
 
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I'd give it a try. I don't think ducks will always bring parasites, but they definitely can. In may have been a case of "correlation implying causation" but it was the only thing we could pinpoint that was different from prior years. The fish did not all die at once - which would have pointed to some kind of contamination issue. Fish of all sizes were dying, so it wasn't oxygen deprivation. And the way it was going from fish to fish just seemed to point to something that they were catching from each other. Our best guess was some kind of parasite, so we went with Prazipro and it seemed to be the answer.

From my reading, Prazipro is relatively free of any kind of unintended side effects. It was easy to use and in our case worked rapidly.

We ordered ours from Amazon.
 
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great news! I know some people recommend proactively treating with prazipro quarterly if a lot of water birds turn up at your pond. Best wishes!
 

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