new pond, fish got sick and died


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I've had the same 11 goldfish fish in a 100 gallon stock tank for 4 summers / 3 winters. They were free from craigslist so besides the bubblers, filter, heaters for winter, and food, spent almost no $$ on them. Surprised every spring when they were alive and active after the ice melted; I wasn't a very good fish parent, as I didn't do regular water changes except in the early summer.
This summer my we dug a 1200 gallon inground pond (retaining wall blocks as walls, rubber pond liner to keep water in, field and river rocks for the bottom and up the sides a bit). We rinsed the rocks so they weren't completely dirty when we added them. We filled with water and let set for a few days. I had the new pond water and the water from the stock tank tested at the same time at the same pet store and they tested almost identical (no numbers, only color indicators of chemical make up).
I put the old fish in the new pond and they were happy, swam, ate, acted normal. Added a packaged water lily and a few water hycinths. About 4 days later we added 4 small koi from the pet store. About another 3 days later I noticed one of the goldfish began looking fuzzy. We removed the koi; they are in a stock tank and still seem healthy. We couldn't get the recommended water treatment product quickly so relied on stuff from the pet store. Over a few days the goldfish all got fuzzy (slime coming off and got lethargic). It seemed to slow the health decline rate of the goldfish but over 6 days they all, perished, one at a time.
We have now treated the pond with Crystal Clear Knockout Plus for 3 days (1 day without any fish).
What are my next steps... is it something physical in my pond that caused this?
Do I do a water change and add the koi?
How long do fish illnesses remain in the pond after all fish have perished (been removed from water)?
Any direction is greatly appreciated -- and a side note... I love the pond and keeping fish - but I am not really into huge maintenance and I will stick with my remaining 4 little koi. I'm a simple kind of person.
 
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Oh, I'm sorry! It's always sad to lose fish.

It sounds like your new fish brought something with them that affected your old fish. It's generally recommended to quarantine new fish for a few weeks to make sure they are healthy. If you plan to stick with just your four koi, you won't have to worry about that in the future.

Also - "little koi" always makes me laugh. They won't be "little" for long. Your pond is on the small side for four koi, but if you keep your filtration up, keep your pond healthy, they may be just fine. And don't be hard on yourself about the water changes - many of us don't do water changes at all. They aren't necessary for a healthy pond.
 

j.w

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@disi
I have no clue on how long fish disease will stay in a pond. If it were me I might wait a few weeks to add the koi back to the pond just to be safe. Maybe add one at a time or 2 so they have a friend. See how they do for a couple weeks or so and then add the others.
 
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Sorry about your fish.

I have no idea what killed them.

It could be a parasite, I really don't know.

Maybe something was off with your water parameters.
Get yourself an api pond test kit and post up the numbers. It has the liquid reagents, the glass tubes and the charts. Don't buy the test strip type, they are known to be inaccurate.

Can you give us details about your filtration and pump? Maybe your filter is not adequate?

Do you have any plants in your pond to help filter the water?

Try adding a few feeder goldfish before putting your current fish back in.
They are inexpensive and grow up to be nice fish. I have some in there for over ten years, plus their offspring! They were only 10 cents at the time.
 
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I would turn that 100 gallon stock tank into an upflow bog filter. It requires pretty much no maintenance and will just look like another garden with plants growing in and around it.

100 gallons is probably not big enough to filter with exclusively, but it will certainly be very helpful. Who knows, you could always shut the other filter off temporarily and see if the bog alone is sufficient.
It's actually more about surface area when sizing the bog. Generally the goal is for the bog's surface area at 30% of the pond's surface area. If you achieve this, you will only need the bog. You'll never have to rinse filters and filter pads again.
I don't know what the surface area of your stock tank is.
 
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I'm sorry that you lost your fish just as they were getting a beautiful home. Painful mistakes I think are just part of the process. We lost a beloved family pet (a gorgeous extra-long finned 7" comet goldfish that started out as a tiny, humble carnival prize) to a heron one month after I added our fish to the pond and I was sure I had taken all the precautions against it :(

It's possible the fungal infection was introduced to the goldfish by not having quarantined the koi. it's also possible that your new pond is cycling badly (about 5-7 days after adding them would be when you would start to see cycling problems) and the fungal infection was secondary to water problems from introducing a whole bunch of fish all at once to the pond. It's 100% worth buying a liquid (not strips) water testing kit, and once you can make sure the water is stable for Ph, Ammonia and nitrites, perhaps slowly adding the new fish one every few days instead of loading up the pond all at once again and checking the water parameters daily as you go for the first few weeks. You would also definitely want to take a look at Poconojoe's questions regarding your filtration and pump before adding the fish, since getting that right can either set you up for success or a string of problems.

Good luck!
 

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