Lost my whole school today

[VeronicaM]

Yesterday I noticed the koi were a little sluggish and weren't their usual glutton selves. I tested the water and everything looked fine. I assumed it was the heat and just looked in on them every now and again. A storm rolled in later in the day and I could see the koi coming to the top. I thought they were cooling off and it was good to see them active. I stopped worrying and went out to dinner. This morning I woke up and every fish in the pond is dead, the Ph level seems to have tanked. I just dont know what could have caused such a drastic change in ph levels.

Any clues?

V

[JasPR]

First of all, I'm very sorry for your loss. It will hurt for a while but I hope you are able to get back on the horse after some time has passed. And I'm sure you don't want to hear this right now but it is important to know why this happened so that you can learn from this painful lessons and add it to your experience memory bank. Unfortunately, this is how many of us learned koi keeping- one problem at a time.

It sure does sound like a pH crash. But you said you tested the water and it was fine? What was the pH when you tested. And what was the ammonia and the nitrate? What was the water temperature?
How many fish did you have and what is the size of pond? What type of filters do you have? When was the last water change and do you use a prefilter on water entering your pond? JR

[KoiCop]

Hello Veronica . . .

Sorry to hear that you've lost all your koi.

It would appear that you had a classic pH crash where your pond water had insufficient KH (carbonate hardness; also called alkalinity) to buffer (maintain) your pH. When the pH drops rapidly, the koi suffer from acidosis and will die if the balance is not restored.

Here's a bit from Ken Austin (KHA) explaining some of the dynamics:

The understanding of alkalinity (sometimes called kh) requires an understanding of the chemical dynamics of your pond water. When you built your pond, you started out with water, H2O. But, it was not just water. It had some mineral content (mostly calcium, Ca and magnesium, Mg) which showed up when you tested the water for hardness. It also had some carbonates, CO3 and bicarbonates, HCO3, which showed up when you tested the water for alkalinity.

Then you added fish and the first thing the fish started doing was consuming the oxygen, O2 from the water and replacing it with carbon dioxide, CO2. At night time, when photosynthesis can not happen, plants are also adding CO2 to the water.

CO2 and water do not mix very well. The water molecule wants to breakup. So, H2O + CO2 become bicarbonate, HCO3 plus a free hydrogen ion called hydronium. The hydronium then reacts with the bicarbonate. to form carbonic acid H2C03. In other words, you now have more acid in your pond and that tends to drive the pH down.

Don’t worry; remember all that mineral content you have in the water? The calcium, which probably exists as calcium carbonate CaCO2, reacts with the carbonic acid to form bicarbonate HCO3 and some free calcium ions. Other similar reactions will occur with a variety of mineral ions that may exist in your pond. Lo and behold, all that acid that was once in your pond is now removed and there is plenty of bicarbonate, which drives the pH back up to where it started from. Adding any other acid (read: any product labeled as pH Down) will do the same thing. It will temporarily drop the pH, but once the acid is completely reacted, the resulting bicarbonate brings the pH right back up.

Does this mean that the acid reaction discussed above will continue producing more and more bicarbonate, which will continue to drive the pH higher and higher? No because bicarbonate has a very stable pH about 8.0 – 8.5. What may drive the pH higher is a hydroxyl ion (one oxygen atom and one hydrogen atom). The abundance of bicarbonate in the water reacts with hydroxyl ions producing water and carbonate.

Carbonate, CO3 also has a very stable pH, but it is much higher than bicarbonate. But again you are in luck. Remember all those calcium ions that were released during the carbonic acid reaction above? The carbonate will react with them creating – you guessed it, calcium carbonate. Once again, bicarbonate becomes the dominant organic carbon in the pond and the pH is stabilized at that nice 8.0 – 8.5 range.

It is important to have a surplus of bicarbonate in your pond to ensure that all acids and all hydroxyl ions are reacted (this is called buffering). This gets us back to measuring alkalinity. Alkalinity is a measurement of how much bicarbonate and carbonate you have in the water. An alkalinity of 80 – 120 ppm is ideal. Koi can tolerate up to 300 ppm alkalinity. As the alkalinity drops below 80 ppm there is a chance that all carbonate will be reacted with acid causing a significant drop in pH to levels below 7.0. This is called a pH crash. Alkalinity levels below 40 ppm are very risky.
Source: Alkalinity and KH.. by Ken Austin

What I'd like to see you test to confirm a pH Crash and not some other dynamic going on:

pH from tap AND from pond
KH from tap AND from pond
GH from tap AND from pond

[JasPR]

Don, you could be right on or you could be making a sweeping error based on the words of Veronica's assumptions. It has been my experience that most hobbyists that loose ponds in a dramatic way begin by suggested that everything was normal and the water was fine before the event. And that could be very true, especially in the case of a pH crash. But 'marrying' a theory early on can be like putting on blinders to the big picture.
A good detective remains uncommitted and dispassionate about theories until the evidence points in a definite direction. And in many cases, getting a diagnosis is as much about eliminating what the problem 'wasn't'.

So in my opinion this problem could be:

) a pH crash
2) a poisoning from natural or un-natural sources
3) suffication
4) a dynamic of disease and environment

Collecting data and history is the best way of eliminating some of these theories and bolstering one over all. - IMHO JR

[KoiCop]

JR . . .

Points well taken -- and I'll be interested to see what we learn.

[gcuss]

no matter what the cause... horrible horrible thing to have happened.

I'm sorry for you. The guys (and gals) on here will definitely be of great assistance in helping you learn, and hopefully prevent this in the future. Try and answer their questions as honestly as you can, and put your best "ears" on. Again, I feel awful for you.

Grant

[Tamianth]

So sorry to read this Veronica...

A full history would be beneficial here, such as how often the pond is maintenaced (Water changes, filters cleaned etc amount of fish) and as Don pointed out, a source test that includes the gh & kh, size of pond . JR also raises some good points, so the questions here would also be along the lines of anyone used any pesticides, herbicides etc recently?

[Lam Nguyen]

So sorry to hear that Veronica. Hope you will recover from this and continue with the hobby. On a side note, a good koi friend of mine also lost all of his koi a couple of days ago. He is a very serious hobbyist with a very serious collection. Apparently someone threw some poison in his pond from outside the fence and he said that within hours all of his koi died. He said that he must have lost close to $50,000 in koi and that he was so frustrated that he almost bulldozed the pond in. Hopefully he will recover from this tragedy.

[JosephandGabby]

Sorry to hear about your loss. We've all been through similar events so we know how this feels. I know from personal experience that PH crashes can be devastating. From you're description, however, I'm not sure what could've caused a crash. I'm assuming it didn't rain the night before and that no tap water was recently added to your pond. In my case, the PH crash was my own fault. Not sure what could've caused yours. JasPR might be onto something here. You should investigate other possible causes before simply assuming it was a PH crash. And no matter what you find out, obviously, you'll want to take precautions to prevent this from occuring again in the future.

[VeronicaM]

My pond is about 2000 gallons. We had twelve koi who have been with us since last summer.
I tested the pond at about 10am. Nitrates were normal, GH was 75, KH was 70 and pH level was 6.8. I use a Cal bio filter, have a waterfall and an aerator. The last water change was two weeks ago. I cleaned the filter on Saturday afternoon. I used no chemicals....just washed them off with the hose. The only other thing I can think to mention is the plants dont look so hot either.

Things were actually going really well with the pond. In fact this week several of the fish were spawning. I removed one of the females and put her in a kiddie pool filled with water right from the pond. She laid eggs all over the aerator and artificial plants. I waited a day and put her back in. Some of the other female look bloated so I took them out as well but when nothing happened after three days I put them back in the pond.

I suppose I just feel totally defeated. I spent to much time working on the pond and caring for those fish. They brought so much serenity to my life.

Vee

Originally Posted by JasPR

First of all, I'm very sorry for your loss. It will hurt for a while but I hope you are able to get back on the horse after some time has passed. And I'm sure you don't want to hear this right now but it is important to know why this happened so that you can learn from this painful lessons and add it to your experience memory bank. Unfortunately, this is how many of us learned koi keeping- one problem at a time.

It sure does sound like a pH crash. But you said you tested the water and it was fine? What was the pH when you tested. And what was the ammonia and the nitrate? What was the water temperature?
How many fish did you have and what is the size of pond? What type of filters do you have? When was the last water change and do you use a prefilter on water entering your pond? JR