Koi died - high phosphate


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Good Morning,

We moved into our house in February and today had our first dead fish :(. I immediately tested the water (drops) and the levels are fine besides Phosphate which is high (5). Ammonia 0, Nitrate 0, Ph 7.

We added sludge destroyer because that’s what the water test instructions said.

Normally the Phosphate was around 2.

Things that happened: lots of rain over the summer, storm yesterday with lightning and rain. We are in zone 7.

We feed 1x day what they eat in about 2-3 min (8-10 hand fulls of pellets).

What should I do to lower the Phosphate? We are planning to clean / cut back the plants soon for winter. They are still green. Should we do it now or wait?

The bottom of the 4500 GAL pond is filled with stones, we have one waterfall and one pressure filter w UV-pump is at bottom of pond, 2 airators and a skimmer w prefilter and pump that feeds into waterfall (w filter and bioballs and lava rock).

We clean the prefilter every 2 days and waterfall weekly to every 2 weeks.

We have a lot of larger Koi and they had babies in the summer that are a few inches only.

The fish that died was about 12 inches and did not look injured. Not sure how old.

Thank you for your help!

Regina
 

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Welcome @Regina to the GPF! Sorry that it's pond trouble that brings you here, but we hope you'll get it figured out and stick around!

Thanks for sharing all the pertinent details - one more would be useful: how many fish? You have a sizeable pond, so I doubt it's an overstocking problem, but if you come back and say you have 60 large koi, that might be an issue!

I'm not a water testing expert - we have others here that are more versed in water chemistry who will chime in. @MitchM - are you around?
 
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I just looked at your pictures - are you sure about the size of your pond? It's hard to tell scale from photos, but it doesn't look like a 4500 gallon pond. What's the width, length, and depth?
 
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Lethal phosphorus concentrations for carp are around 500 ppm, not 5 ppm.
Can the OP tell us what test kit was used, if the sludge destroyer is used regularly and if there are any other test numbers available?
KH, GH?
Phosphate levels can be reduced by water changes, plants or a phosphate binder.
(Phosphorus is the element, phosphate is a compound containing phosphorus) The terms are sometimes used interchangeably.
 
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I used the API pont test kit and it was the blue level (medium blue not dark blue) for phosphate. It says it is caused by decaying plants / fish food and water runoff.

The pond is about 16x20 feet and 3 feet deep.

We are having trouble counting the Koi because they keep swimming/hiding. The highest we counted was 20 plus a few babies.

We used the sludge remover 2x this year, once in March and once today. 22 scoops.

Thanks,
Regina
 
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Mmathis

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I just looked at your pictures - are you sure about the size of your pond? It's hard to tell scale from photos, but it doesn't look like a 4500 gallon pond. What's the width, length, and depth?
In another post OP stated pond was about 15x20 and 12”-30” deep. It did look larger in the older pics, though.

Nice pond, @Regina. One thing to keep in mind — sometimes fish die for no apparent reason. You always want to try to the best of your ability to ID the cause, though, as you have done by checking your water parameters, and of course, always stay on top of water quality.

That random fish-death was a hard concept for me at first — and it still is. But sometimes it just happens, and not from anything we have done wrong. I wanted to throw that in there.
 
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I just looked at your pictures - are you sure about the size of your pond? It's hard to tell scale from photos, but it doesn't look like a 4500 gallon pond. What's the width, length, and depth?
I think we miscalculated the GAL - maybe it is only 2500. I have to look at the measurements again.
 
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Like @Mmathis said, sometimes our fish die from natural causes.
I do think you should have a KH/GH test kit on hand as you mentioned you have a PH of 7 and you can have a lot of rainfall. If you have some large PH swings, combined with a low oxygen level from a lot of fish and perhaps a fair amount of decaying matter as well as using a product like Sludge destroyer, weaker fish can succumb to less than perfect water conditions. An O2 test kit wouldn't hurt either. The extra kits are not that expensive and will give you a better understanding of your pond's water quality.
 
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The pond is about 16x20 feet and 3 feet deep

Hmmm... I think that would be more like 7000 gallons. Maybe check again. It is important if you are adding any kind of chemicals or water treatment to know how many gallons you are dealing with.
 
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Hmmm... I think that would be more like 7000 gallons. Maybe check again. It is important if you are adding any kind of chemicals or water treatment to know how many gallons you are dealing with.
It is 15x20 feet and 2.5 feet deep (oval shape).
 
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In another post OP stated pond was about 15x20 and 12”-30” deep. It did look larger in the older pics, though.

Nice pond, @Regina. One thing to keep in mind — sometimes fish die for no apparent reason. You always want to try to the best of your ability to ID the cause, though, as you have done by checking your water parameters, and of course, always stay on top of water quality.

That random fish-death was a hard concept for me at first — and it still is. But sometimes it just happens, and not from anything we have done wrong. I wanted to throw that in there.
Thanks! The pond looks smaller because the plants are growing now. There is about 1 foot of plants overhanging the pond on one side (fish like to hide unter it).
 
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Thanks! The pond looks smaller because the plants are growing now. There is about 1 foot of plants overhanging the pond on one side (fish like to hide unter it).
Hi Regina. I'm sorry about your fish. Was it sudden death or did you see it sick for a while? If it was sudden there may not be enough dissolved O2 in your pond, What is fine when your fish were younger and smaller may not always be okay when they grow. Also just a comment about feeding. It's always better to feed more frequently smaller amounts than one big feeding. I'm not sure how many fish you have, but 8-10 handfuls at once sounds like a lot.
 

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