Hi there,
I wrote back in May needing some help understanding why my fish were dying after the our pond started to warm up. I thank you for your help in that case. I'm here again with much similar events.

I just got home from work and my husband told me that he thinks that we had a dead fish at the bottom of the pond. Sure enough, one of our big fish was dead. It was lying underneath one of our flower pots that was slightly floating off the bottom. Then I saw not one but two of my medium size goldfish floating amist the leaves of my cattails. So I pulled out all my pants and there was my other large goldfish. He isn't exactly floating on his side but immobile. I can't believe it.
The weather here is starting to get colder so I haven't been feeding them as frequently, probably every other day or so. We have had our pond for several winters and this is the only time we lost fish this time of the year. Any ideas on why my fish are dying.......again? Again, any help would be greatly appreciated.

I'm sorry about your fish. Have you tested the water for pH, hardness, ammonia, nitrite, etc.? Do they have any other symptoms aside from lethargy and death? What things do you add to the water? Not knowing what is wrong, a 20% water change probably won't hurt (unless the tap water is bad) with added dechlorinator and pond salt to 0.05%.

This section on my site lists reasons fish may die. You may want to go through the list and see which might be possible.

http://www.fishpondinfo.com/health4.htm#why

Hi Robyn,
Thanks for replying to my question so quickly, but it is too late. All my fish are dead. Last night's immobile fish was a floater this morning. While looking for the rest of my small fish, we found our one and only shurbumkin in a fold. Not sure how long he was there for I haven't seen him lately. When I fed the fish on Sunday, all fish came vigorously but I didn't see him. He was a little hard to see for he was black and the only time you really caught a glimse was when he swam in front of a goldfish. (He was a fish that outgrew my nephew's tank therefore we put him in our pond last summer). We are figuring him being dead in the pond for an unknown length of time may have affect the other fish or if some children in the neighbourhood were a little mishchief. As for a water exchange, no need, for we have had some heavy rain here off and on for about all week. The other cause my be the change in temperature. I don't think it was a quick change in temp, but then again I'm not a fish.
Thanks again, but we will start all over again next summer. Well we won't have to worry about overwintering.

MJ

That's horrible! You've got to find out what happened. How big is your pond? How many fish did you lose/have? Did you test any of the water parameters? A fish dying in the pond almost never causes an entire pond to die off. Neither would a somewhat fast change in temperature which can be stressful. Too much rain can cause a pond to die off if the pond is small. Rain will lower the pH, hardness, and oxygen levels. If you could have tested those at the time the fish were dying (and right before that), that may have given us a clue as to what happened.

I'm so sorry. :(

Thanks Robyn,
We lost 2 large Godfish and one large Shurbumkin all measuring between 8-9 inches long as well as 2 medium goldfish, about 3-4 inches. I'm still missing 2 goldfish, I can't find them anywhere. They haven't come to the surface, I've removed all my plants and peeked in the folds of the liner and found nothing. Unfortunately we didn't test the water when this happened. The weather here has been really miserable, cold and raining. Besides I was working Monday and Tuesday with my husband home with our 18 month old. I don't know about the men you know, but mine isn't very good and multi-tasking. It was after 10 o'clock at night in the pouring rain that I went and scooped up the dead fish and removed all my plants. I didn't test the water because there was only one very immobile fish left. and I'm out of testing material. I really didn't think I needed it this time of year( I still have alot to learn).
I don't know the exact measurements of our pond but i estimate it 4.5 ft across , 7 ft long and about 3.5 feet at its deepest point. i believe well able to handle the amount of fish we had. So if a dead fish decomposing didn't do it, the amount of rain didn't do, the change in temperature isn't responsible, I may be looking at some act of mischief from someone. I can't see it being an amonia level or nitrate because that was the reason for my lost fish last spring. That was a slow, noticable death. This was faster. The fish were fine on Monday afternoon and Tuesday afternoon, dead. I'm just at a lost. Hopefully when i start back up next spring, I just may get it right. It just gets me mad, I have friends with ponds and they do absolutely nothing with there ponds. don't check the water nor add salt, or chemicals and they have had their fish for years. We have lost so many fish, its retarded. We now just buy the cheapest goldfish we can find. ..... anyway enough from me. Thanks again for your advise. Much appreciate it......MJ

You may still want to test the water now to see what the values are and if they're reasonable. Poisoning is a possibility. It could be directly from someone putting something in the water or indirectly such as pesticides/herbicides/fertilizers runnning off of someone's land into your pond during the heavy rains. I hope you have better luck next time.