My hubby did a waterchange yesterday on his main temporary pond (about 3000 gl above ground), and forgot to take the waterhose out before he went to bed. Which means constant chlorine/chloramine exposure all night long. When we got out this morning, wanting to check on our spawning koi in the spawning pond, there were 8 dead koi in the pond and 2 clearly not acting right. Boy, talking about your idea of a saturday morning....

I immediately dumped a good 1 1/2 l of Prime into the pond, which is good for about 15.000 gl of water. One good thing about it was that a hose to one of the filters must have come off sometime at night, and that filter wasn't exposed to chlorine as much as the other one, but I still don't want to know how much of the beneficial bacteria has died off or suffered. We added tons of extra airation in form of powerheads and a 1/6 HP pump that has been converted into a fountain, and I added some salt to help the gills.

Man, I am so upset - my favorite 2 ft yellow butterfly girl was among the dead, our "good luck" koi (all black) and one of my hubby's favorite Sanke. We raised that yellow girl since she was a tiny little thing, and we wanted to spawn her the next couple of days. Stupid, Stupid, STUPID! At least the 6 koi that were in the spawning pond overnight haven't been affected, and you can clearly tell the difference between the fish - they breathe nice and slow, while the chlorine exposed fish breathe really heavy. Poor things - only time will tell how much damage has been done.
Hubby researched a bit on the internet tonight, and it turns out that the most reason for a large koi die-off is the hose forgotten in the pond. Looks like many koi die that way, and I just wish even more now that we would have our well water back. We didn't have to worry about that while on a well.... sigh....

Final count: 11 dead, one acting sluggish.

May somebody who reads this learn from it: NEVER take your eyes off of your ponds when doing water changes. DO NOT let yourself get distracted, and leave the cell phone in the house while changing water. Its a hard lesson learned, and I look with sadness at all the beautiful koi we have lost this morning...

I'm so sorry to hear about this. With any luck the others will regain their health in your care.

Is it possible to install a meter/timer on your hose to prevent this in the future? Ive seen these around and was actually planning on putting one on my house line to prevent any more experiences like I had recently with my dechlorinator.

Yeah, they are around, I heard about them this morning. They go for about $ 15, and have a shutoff or something, a timer and an somewhat accurate gollon counter on it of some kind. I definetely will be looking into that, plus the fact that hubby never ever leave the pond when the water is filling in, that is for sure....

Wow Andrea,what a horrible loss for you.It's sad how it sometimes takes awful situations like this to happen,to make us more aware.Why do "lessons learned" have to be so tough?
I really hope that the rest of the fish pull through it for you.

Thanks, Sharon - yes, I hope so too. One more fish dead, a smaller Tancho...

Although I have been told not to feed the fish for the next few days until the bacteria has catched up again, I see my hubby feeding them already a small amount. He felt sorry for the begging fish which weren't in the compromised pond last night. I told him not to do it...

I am so sorry Andrea! What a horrible way to lose fish.. and so many! I hope the others get well after that.

Andrea,

I'm so sorry to hear about this. Poor fish.

The same thing happened to me about five years ago. I remembered to shut the water off but I didn't close the valve tight enough so some water was going into the pond all night long. I lost all my fish. Needless to say, I was devastated. I installed a cut-off meter after that. You set it for the number of gallons you want to add to the pond and then it shuts off after that amount.

My condolences.

How's everyone doing today?Any signs of improvements?

I just see this thread.. I am sorry for your koi. I guess cut-off meter is a way to go.

Wow. I'm so sorry you lost so many koi. Don't you just hate it when a bonehead mistake causes so much trouble.

I hope your hubby isn't feeling too guily about something so unintentional.

Oh Andrea! That's horrible! I'm so sorry to hear about your koi, what a huge loss for one small mistake. God, I'm so emotional at the moment, I'm actually crying... poor fish, koi are so beautiful....

Thanks guys - koi say "thank you" too....

No losses today, and their breathing has become considerably slower and almost back to normal. Although I will not hold my breath just yet - their could be secondary things popping up in the weeks to come.

Fish all came begging for food today, and they only got a fraction of what they usually would get, but safety has to be first. Hubby was very upset about it yesterday, since they are mostly his pets. He raised most of them from small 4 inch fish, and its hard on him. I am very sad about my favorite fish though, she was a huge beauty. I am a dead ringer for longfinned anything, and she was a beautiful butterfly koi.

Sonny, that cut-off divice is a great tool, huh? Next thing that comes into the house, that is for sure...

I am so sorry Andrea. Makes me thankful that I have well water and don't have to worry about those things if the hose gets left in too long.

Sorry I missed this and I am so sorry you loss so many Koi! That was a horrible accident and I hope that you both are doing alright, as it was an accident. I know your husband must have felt really bad, but he needs to know it was something he did not do intentionally.

So sorry, I'll keep my fingers crossed that the rest are ok

one more thing, we have a auto fill installed in our pond. I have no idea what that cost but it works great giving a little water at a time when the level goes down. Maybe you can install one.

So sorry to hear about the loss of kois. It is truly depressing. :-( I have been there before. I lost almost all my fishes some time back. Although that was because of my negligence in not properly dosing algaefix. *sigh* Sometimes those poor little things pay with their lives for our mistakes. I hope you feel better.

Andrea,
So sorry to hear about your losses but something like that is so common even amongst the great koi keepers. I know this don't help you, but I have heard the stories of koi keepers losing tens of thousands of dollars worth of show koi for the same reason. Like they say..shizzit happens.
Personally I have forgotten my fill line on occasion but my water is treated by a huge carbon filter. It might be something looking into to. Mine was a few hundred bucks but it treats the entire house and I only change the carbon every two years. Even after two years it still read zero for total and free chlorine....but I felt it was time to change anyways. Better safe than sorry for my case.
Regarding your fish...you might want too pull a couple up and check the gills. That should give you a good barometer of how much damage was caused. If they still look like bloody steak you should be OK, but if they are burned you might have some ongoing problems depending on how fried they are. I'm assuming they will be burned to a degree. It just matters how bad for their long term survival. And keep that air going as much as you can....boil the water if you can.

So sorry to read this Andrea!

A lesson for all and shows even the best of us have problems and accident's and loose a few sadly!

Big hugs my friend!