Death of fish and some plants


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Good evening. A couple of days ago my husband put some algaecide in the pond. I was also placing rocks that I had finally bought. I was washing rocks to get dirt off before placing in the pond. I was having to get in it to place them. It is approximately 10 feet by 13 feet.
within about 10 minutes of putting the algaecide in, fish started dying. All 15 fish, goldfish and koi have died. In the couple of days since, my water lettuce and hychaniths are looking yellow.
The ph is more 6.5, ammonia it’s .25, nitrates are 0, and phosphates are .25.
Needless to say we are devastated at this, but need advice on how to proceed. I am not getting any fish, though I needed some plants to provide shade.
What do I need to do to return it to health?
I used a drop test kit, not strips. I had replaced all of the water a few weeks ago and waited 24 hours to put fish back. They were fine at that time.
 
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mrsclem

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So sorry to hear this. So many pond owners take the shortcut to rid their pond of algae. Often this is the result. No chemicals other than a dechlorinator if needed. Were those test results before or after the algaecide? Your plants may have been affected by the algaecide but should recover.
 

j.w

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@Deanna Gupton
Sorry you learned a lesson the sad way. I never use algaecide in the pond. Too many times we hear the same sad ending.
 

Mmathis

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Hello and welcome! Sorry to hear about your fish — that’s always devastating!

If you stick around here long enough, you will find that most of us don’t use chemicals (with exception of de-chlorinator). Algae is part of the pond ecosystem, so we tend to look for natural ways of keeping it in check. Algae is not bad, but it can be an indicator that you have too many nutrients in the water. This is usually seen especially with new ponds, if the pond hasn’t cycled yet.
 
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So sorry to hear this. So many pond owners take the shortcut to rid their pond of algae. Often this is the result. No chemicals other than a dechlorinator if needed. Were those test results before or after the algaecide? Your plants may have been affected by the algaecide but should recover.
Thank you. The test results are from today. I plan to get a few more plants, but think I’ll wait on more fish for awhile.
 
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Hi and welcome. I’m sorry about you losing your fish. Almost all of us have learned the hard way how to take care of a pond and fish. I agree with comments above. Actually algae is your friend because it will eat the excess nutrients and ammonia that would otherwise kill your fish. It takes a while for a pond to naturally cycle. If you put fish back just go with a few small fish until your pond cycles and the algae goes mostly away. If you are not familiar with the nitrogen cycle there are a lot of threads here that discuss it. Basically you are implementing a way for all waste products to be naturally converted to mostly insert substances... ie ammonia to nitrite to nitrate and then the nitrate is used up by your plants. There are two types of beneficial bacteria that are part of this process and it’s best if you have a biological filter to grow them. Again you don’t need to buy the beneficial bacteria if done properly. At some point the algae will die and go away because there is nothing for it to feed on because the bb is eating all the nutrients that were feeding the algae. This will all be done with no chemicals other than declor to treat the water you add to your pond. It takes some time for this all to happen and it’s very common that there is a lot of algae in the first few months of a new pond. Good luck!
 
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addy1

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Welcome to our forum!

All above said what I would have said. Plants are your friends in ponds, my system is filtered with just plants , in the pond and in the bog. Let the pond sit for awhile, maybe even do some water changes then get more fish.

I didn't see what size your pond is, if under 2000 gallons I would not get more koi, stick with goldfish, shubunkins. Koi demand a lot of water and great filtration.
 
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Hi and welcome. I’m sorry about you losing your fish. Almost all of us have learned the hard way how to take care of a pond and fish. I agree with comments above. Actually algae is your friend because it will eat the excess nutrients and ammonia that would otherwise kill your fish. It takes a while for a pond to naturally cycle. If you put fish back just go with a few small fish until your pond cycles and the algae goes mostly away. If you are not familiar with the nitrogen cycle there are a lot of threads here that discuss it. Basically you are implementing a way for all waste products to be naturally converted to mostly insert substances... ie ammonia to nitrite to nitrate and then the nitrate is used up by your plants. There are two types of beneficial bacteria that are part of this process and it’s best if you have a biological filter to grow them. Again you don’t need to buy the beneficial bacteria if done properly. At some point the algae will die and go away because there is nothing for it to feed on because the bb is eating all the nutrients that were feeding the algae. This will all be done with no chemicals other than declor to treat the water you add to your pond. It takes some time for this all to happen and it’s very common that there is a lot of algae in the first few months of a new pond. Good luck!
Thank you!
 
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Mmathis

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2000+ gallons. I just drained it, cleaned it, (water only) and refilled it about a month ago.
When you said you “cleaned it,” what exactly did you do? If you washed off all of the biofilm, the pond would have to completely recycle, starting from scratch (as per @CometKeith’s explanation). That might have been the reason you had an algae bloom in the first place.

We are always learning. Hope you will stick around and share your journey with us!
 
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Welcome @Deanna Gupton ! We have heard that same story so many times, unfortunately. Often the trouble begins as yours did, with a total clean out. That's not something that is really necessary, but if you do choose to do it the best idea is to keep as much of the water from the pond as possible to refill with once you're done. Mature pond water is like fine wine... the best stuff there is! And then you clean out the pond, start with fresh water and BOOM algae bloom. That's nature's way of giving you a hand by the way, and will happen like clockwork. Sadly we've been conditioned to believe algae is a problem that has to be "treated" in a pond, instead of seeing it for what it is - a protection for our fish until the pond gets balanced.
 
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Your pH is in the acidic range so the beneficial bacteria that needs to grow for the nitrogen cycle will have a difficult time getting established. It will also be hard for plants and fish to thrive at that pH level.

Do you know what the pH was before the algaecide was added? I suspect you had a pH crash that killed your fish and the benificial bacteria in your system.

I would recommend you get a liquid test for KH if you don't already have one and testing your KH. My guess is that you have little to none.

KH keeps the pH stable so it won't crash. If the level is low you can add baking soda to raise the KH and the pH. If there are no fish left in the pond you can do that quickly. If there fish you should do it gradually. The KH level should be 100 to 200 ppm.

Sorry for the loss of the fish. I hope you get things stabilized soon.
 
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Agree with @addy1 about koi.

How many gallons is your pond, and how long has it been up and running?
It is 2500 gallons. I drained it a few weeks ago because there was so much muck that we couldn’t get under control. We made A LOT of mistakes in this process. I’m appreciative for this group. I’m learning a great deal.
 

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