Koi died after water change

[BrentG]

Hi all,
Yesterday I cleaned my koi pond as I do every spring/summer. I simply drain it, put the koi in a kiddie pool and then clean out the pond. I filled it back up with tap water as usual and then put the 3 koi back in along with large goldfish we got several years ago. I've done the same process every year for 5 years. I did this at about 4pm yesterday. This morning, my pump had kicked off during the night for some reason and the 3 koi are dead but the goldfish is alive. I didn't add back any existing water as usual. Any thoughts on what happened?

 

[Lisak1]

Welcome @BrentG - sorry to hear about your koi. That's always hard. Maybe we can help you figure out what happened and then you can stick around and share happier pond days with us!

Here are some initial thoughts - you refilled the pond with tap water. Did you add a dechlorinator? Chlorine will kill fish. Your pump went off - that could have lead to low oxygen in the pond. When big fish die overnight you usually assume low oxygen. Water changes can also be stressful for fish. I personally am not a believer in routine water changes. Filling a pond with fresh water means starting all over with the nitrogen cycle - also hard on fish. So it may be that you had a combination of factors that stressed your fish. I know you said you've done this routine every year, but bigger fish can be hit harder by stressors. And it may be that your fish were already at the tipping point - too many fish in too small of a pond, for example - and the events of yesterday just put them over the edge.

Tell us a bit more about your pond - how many gallons? How many koi did you have? How big were they? What kind of filtration do you use? Do you have plants in the pond? Pictures are always helpful.

 

[j.w]

@BrentG

Sorry for the loss of your koi. I agree w/Lisa on not cleaning out your pond totally like you have been doing each year. That's a real shock to the fish who were used to the old water. If you are scrubbing the sides of the pond you are taking off all that good growth of good algae and all the good bacteria that have accumulated. Your filter should be good enough to keep the water clean enough for the fish. Just top off the pond w/water when needed and use a net to clean out any gunk from the bottom or floating on top. That existing water that you usually add back into your pond could be what have saved your fish from dying each year and w/the pump going out that was not good either. We all learn as we go.

 

[bettasngoldfish]

"Filling a pond with fresh water means starting all over with the nitrogen cycle "

@lisak I just want to clarify this statement. You are not the only person on the forum that has made similar statements lately and I feel I need to say this...

Changing water has nothing to do with the cycling of a pond or an aquarium. It's the filter and all the good bacteria that lives on the media that make the water safe for fish (good bacteria also live on the pond liner, any rocks or stones, etc) you can change as much water as you want and it should not affect the cycle (so long as you are using matured filter/media and dechlor with water change)

If your statement were true I would have big trouble with my own aquariums and ponds (currently 21 tanks and 2 small ponds) most all of my tanks get routine large water changes. I have yet to see my cycle crash/start over from doing tank/pond maintenance this way.

I do agree with the rest of your post.

 

[Lisak1]

Changing water has nothing to do with the cycling of a pond or an aquarium.

You are correct - I should have said that emptying, cleaning and then refilling a pond COULD eliminate everything beneficial in a pond, depending on how thorough the cleaning is - especially if you add chlorinated tap water to the equation. Far better to save as much pond water as possible and avoid the urge to scrub the pond clean!

Thanks for the correction!

 

[GBBUDD]

I do believe in water changes at specific times, such as after the winter thaw. if you shut down your pond for the winter that water is less than ideal. As the fish are coming out of a state where they are a step away from , it is easy to shock them with a drastic water change. but if it is done right i see it a a benefit and not a detriment. But i do have a larger pond and changing some water can be done with next to no parameters changed drastically

 

[Lisak1]

But i do have a larger pond

I think that's such an important point... size is important, set up is important, fish load is important. Every pond is different. I just think it's important for people to read about different methods and viewpoints. When we first started keeping a pond, most of what I read was very cut and dried - not a lot of variation. Then I started to recognize that a lot of people came to pond keeping from the aquarium world and carried those practices over into pond keeping. Some things are the same, but some are very different.

 

[C-Note]

My best guess would be not enough oxygen because of the pump going off. Especially because the larger fish died and the smaller did not, which is exactly the pecking order for oxygen depletion. Regardless, I am very, very sorry that you lost the fish. I find that so heartbreaking when it clearly sounds like you've been taking great care of them for 5 years.

 

[Mmathis]

@Earsom This thread is 2 years old and the OP never came back after he/she made this post.

 

[MimsBird]

Hi all,
Yesterday I cleaned my koi pond as I do every spring/summer. I simply drain it, put the koi in a kiddie pool and then clean out the pond. I filled it back up with tap water as usual and then put the 3 koi back in along with large goldfish we got several years ago. I've done the same process every year for 5 years. I did this at about 4pm yesterday. This morning, my pump had kicked off during the night for some reason and the 3 koi are dead but the goldfish is alive. I didn't add back any existing water as usual. Any thoughts on what happened?

 

[MimsBird]

The same thing is happening to me right now. When I got these baby Koi at the pet store a few weeks ago, I had freshly cleaned my pond but I had waited about three days before going and getting fish, with the filtration waterfall running constantly, all the while. . I’m sure that any chlorine etc. in the water had dissipated in that time. It also had some time for the water to go through the bio balls and other filtration media reestablishing good diatoms and beneficial bacteria. Now, I’m watching each of the five baby koiI tick off, one at a time. I feel absolutely sick to my stomach.

But I did find this website and I bought just about everything they are suggesting on it. Next time around I’m never going to replace more than a quarter of the water and no more than every 2 to 4 weeks. I’ll also be using a huge activated carbon filter on my hose when filling the pond with that much new water.

Some of these dechlorination/water conditioning products listed on this page are safe enough to add even with fish in the water. So, I’m thinking a little of that, along with the polish brand activated carbon in the waterfall weir, plus the bazooka hose attachment filter, I think I’m going to be less likely to lose koi next time around.

Even though these were small baby koi and I’d only had them for a few weeks, I had already named one after my late cat Wanda, who passed in December of 2020, at 18 1/2 years old. So this made me really sick and sad to lose these-especially when “Wanda” was the first one I lost today.

Just sickening.

So I can imagine what you went through after taking care of your koi for five years. My heart goes out to you even though now it’s something that happened in the past and I’m just now stumbling upon this forum, years after the fact..

God bless you and thank you for starting this discussion. It is a painful and hard won but if knowledge. We just didn’t know until we learned the hard way.

Painful.

Hugs,
Cynthia

 

[MimsBird]

@Earsom This thread is 2 years old and the OP never came back after he/she made this post.

I bet she wanted to forget about it just as soon as she could. That must be hard losing five-year-old Koi

 

[poconojoe]

I never do water changes, but you can get away with doing that if you do it correctly.

The biggest point is that doing a complete drain and scrub is really bad. Especially the scrubbing or power washing.
That existing water is liquid gold. It contains everything the fish need for a healthy existence.
It's not just the beneficial bacteria and biofilm you are getting rid of, but there's also many microorganisms that are part of the ecosystem. Fish cannot survive in a sterile environment.

I agree that the size of the pond is a huge factor. A small pond reacts to changes quicker and more detrimental than a bigger pond.
If your pond is overstocked with fish, that's a big concern and makes things exponentially worse.

The same water has been in my pond for years. Nature adds to my pond when it rains. I can see if you live in an area where there isn't much rain and you suffer with severe evaporation. In that case, you may need to add water. If your home's water is chlorinated, you need to add the proper treatment.

 

[Mmathis]

@MimsBird This is an old thread, and the OP never got back with us after making this first post.

 

[Dave Cee]

An additional consideration for ponders using municipal water supply to fill and/or refill ponds, especially in the U.S....
In compliance with strict federal regulations, municipal water works may add chlorine and/chloromines to your tap water at any time and without advance notification, for mitigation of "short term" water quality problems. Water that was safe last week may harm your pond fish this week. And then be safe again a few weeks later. Just be safe...your fish trust you!
Best wishes. Dave