I'm sorry to hear about your fish. I love my koi, so I can only imagine what you're going through.

It's difficult to say without knowing exactly what the water parameters were. You had a lot of large fish in a pond that size, but if your son had the water tested and everything was fine, then your filter must have been able to keep up with the load and I doubt that is your problem. Something happened, but it sounds like it was sudden, whatever it was. The fish would probably have been showing signs of distress if it was an ammonia build-up, i.e. gills pumping, red streaks in the fins, fins clamped, lethargic, etc. Can't rule it out, but my guess it was something else.

Was there any spraying going on in the yard or the neighborhood, such as spraying for mosquitoes, or using any other bug spray of weed spray? Those things sometimes leech into ponds and can cause mass-kills. I have a neighbor that sprays her trees for bag-worms, so I keep a sheet of plastic handy to pull over the pond to keep any from blowing in the pond.

Teens and parties just seem to go hand in hand, don't they? I'm sure your son is positive that nothing happened, but it is possible that something happened while his back was turned. It's impossible to watch everyone at the same time, and some people are just malicious. Could some of them tossed their cigarettes into the pond or some other noxious substance?

I'm sure others will come up with some ideas, but unless someone "fesses up", I'm not sure you'll ever know exactly what happened.

Thanks, nancy, for your fast response. Though I found out this past weekend, I still find that I am just so stuck in moving forward. I realize that I will probably never really know...and that makes the loss that much harder.

No spraying that I know of...the pond was not in a location that would get runoff unless it was from *our* yard - though I guess overspray could be...

Logic tells me that something was put into the pond...it just all seems to sudden to have not had *any* problems or signs prior.

But WHAT?

The most obvious thought would be alcohol - or urine.

It would seem that the urine would show on a typical water test, wouldn't it?

And would alcohol have that kind of affect? I mean...it seems like it would take *quite* a bit of it, no?

Son seems genuinely perplexed...but you know how parties can get. Like you said...I doubt he was able to watch everybody. (And trust me...I am REALLY refraining from expressing any further feeling that I have about that whole situation!)

I guess I just want to make sure that there are not any other more "natural" things that could have happen...something that really might not be his fault - especially considering just how very upset I am with him right now.

I don't know what effect alcohol would have on a pond or the fish. Urine would probably cause an ammonia spike, but to overload a healthy bio-filter I would think it would need to be more than just one person contributing.

This is puzzling, to say the least.

Hi,
Last year my neighbor had the hedge sprayed, I would have never known if the company that did it was not decent. They left a note to let me know, they had started at the front of the property and did not realize until they got close to the pond... luckily the fish were not hurt but the plants did not do well. You never know. I can not think of anything that would immediately affect the fish, given the concentrations that would be needed, I can't see kids throwing that much alcohol into the pond. the only thing I can think of would be something going into the pond, like a frisbee or a ball that had been into a pesticide, but even then the concentration needed to affect the pond. One thought I have is that it may have been stress, loud music would cause vibrations and a lot of unusual movement and lights may have stressed the fish. I have seen fish just die from being chased in my aquariums. Sounds like you have a basically good kid who is genuinely sorry for the pain you are in. Sympathies, sorry I couldn't be more helpful

The whole thing is terrible, the loss of trust the most. You may find you want to talk to someone about that. I don't know your son but it may be that he is feeling pretty devastated, too.
I can't imagine the donation of one or even several could raise toxic levels in such a large amount of water. My bet, some one of the "guests" discovered the fish begging for food and proceeded to toss in the closest thing, a cigarette, which would have come apart easily in the water. Other cigarettes probably followed since to a drunk or to a teen who has no notion of consequences thought it was hilarious to see the fish beg the way they do. Filters from butts would have been horribly toxic, small bits of tobacco the same for smaller fish. How do I know? The men who were supposed to be putting a new roof on our house thought it was funny when they tossed their cigarette butts into the pond. I was near enough to retrieve them before too much damage was done. I lost only two small koi I had just put in the pond. Both rushed to nibble and they were gone in minutes. The men didn't even have the excuse of being drunk or filled with party excitement or teenage hormone surges. There were other things that might have found their way into the pond such as salty foods but such a huge kill needed something more toxic. Nicotine is about the only poison that could do it that fast or that completely.
To give your son the benefit of a doubt, he might not have seen what was happening at all. I know my sons sometimes had friends they discovered were not good for them. That is a lesson most of us have to learn on our own and we are lucky if the price is not too great.
I hope you can find trust again. Sandy

All the ideas and experiences help....thank you.

You never know when one will click with something else I might have noticed but not connected.

I had always heard that these kinds of things are almost always a part of a ponder's experience - at some point in time. But it sure makes it hard to start over...

There are some changes that I've long wanted to make in the pond - ie, a REAL bottom drain - but was fearful to do it because of having to move the fish. So...I'm trying to get myself excited about this as an opportunity...but it's still so hard. :(

Fishhooked,
I would say that it was one of two sources. Poisons being sprayed in the air. It could have been as accidental as someone spraying for mosquitoes on the patio. Or someone using mosquitoes repellent on themselves and than putting their hands in the pond. In which case your son may not have put two and two together. Anything else such as cigarettes your son would have seen signs the next day and would know what caused it. In this case he may not want to tell you. So the question is do you believe your son? If you do than the answer is that it probably was accidental. It may have been caused by the party but it would be accidental. In any case you may never know.
Mike

Cigarette theory is a very good one. Teens do stupid destructive things to entertain themselves. I found a kid from down our street (18 years old) spitting in our pond to see if the fish would eat it. I can't even tell you how furious I was at him. Additionally I couldn't believe someone who I thought had the same love and respect for the environment would do something like that - but he did. Why? To show off to a 7-year old.
At any rate, your fish were definitely poisoned. The question becomes, what kind of poison? IÂm not sure alcohol would have the concentration needed, but there are other things a person keeps in the house and in the garage that could have done it. A little bleach, toilet cleaner, lighter fluid, weed sprays etc. If there was no insecticidal/pesticidal spraying with a lot of rain to wash the chemicals into the pond (that day), then it is 100% something the kids did. Keep in mind, often the host of a party will not have control of everyone there, so he truly may not know what people poured or tossed in there.
If I were you and it were my kid, I would tell him you did extensive research on-line and have determined it was something someone added at the party. If he throws a party he needs to accept responsibility for the actions of the people that attend. The ramifications of the fact he has irresponsible people attending his party, is it raises the likelihood of someone driving from his party (your house) while tipsy or drunk and then getting in an accident hurting or killing someone. Each State varies, but an incidence like that would make him (and you by proxy) liable. Teens being what they are tend to learn the hard way and maybe this is his wake-up call.
Though we always wash our hands after applying mosquito spray, I highly doubt that could have been the cause unless they were spraying it straight into the pond. One again, people do stupid things when they're drunk and in crowds.
My background is from the University of Michigan in Microbiology, Genetics, and Ecology. So I do know a thing or two about this :)

Thank you all for the replies.

I realize that I will probably never know...and that makes it even that much more difficult to accept such an utter loss. But my suspicions have been toward son...and the friends that he had over...and my inclination has been to hold him responsible (whether malicious or not, whether he knows exactly WHAT happened or not).

He has just been adament that he nor his friends had anything to do with the pond....and not having lost many fish before, I just needed to be sure that I was (more probable than not) accurate in my assessment of the situation.

I visited my local pond store and had every test they can do done on both the old water (son saved a sample supposedly) and the new. Both tests came out with exceptionally clean water - as they always do. (And I'm glad to know that the pond was/is working as it should.) They were also adament that something had to be put in the pond...and we ran through every scenario they could think of (ie, neighbor spraying, accidental run-off, etc.) and none of them seemed probable (considering location of pond, rainfall at that time, etc.)

The moment that the cigarettes were mentioned, my lightbulb went off. Son smokes - much to my chagrin - so there is NO WAY he would offer up information that cigarettes made their way into the pond. But the number of butts littered around were one of the indicators of the parties. I did tell him that I had had the water tested...and then I also told him that cigarettes were the culprit. The response I got was "Then it may have been my fault" - which I thought was pretty telling. It's the first he has backed down on having any culpability.

I do sincerely thank you all for responding. It has really helped me to garner some ideas on what could have happened...and to see that an established pond is really not likely to crash like this. Without having some idea of what happened, it was hard to consider starting over again.

But I guess we do anyway, don't we?
I don't think I would know how to NOT be a ponder.... :)

Well 2 things come to mind.

1. Kids do stupid stuff. Chances are, he didn't really realize that smokes would kill the fish, and in fact might not have actually put them in the pond (a friend may have).

2. I would suggest that the two of you go pick out some new fish. Unless he intended on killing the pond, as the saying goes "stuff happens" (or another word if you will). Rather than lower the hammer, perhaps you can use this as an opportunity to work with your son to rebuild the pond. I'm not saying no consequences for the party, but don't go overboard.

Again, Kids do stupid things.

I am glad that you are willing to start over. I know that if that happened to me, I would have to start over. But it sure would be hard getting to where I am now with my wet pets. I only have goldies and 2 Koimets, but they are part of my family and I get so much enjoyment out of them. Just as a FYI: If your pond gets contaminated from someone spraying insecticide and you have it handy. Koi Clay is supposed to help neutralize the poison. Gene at Koi Village recommends this. I would check with him.