Yesterday morning was very upsetting. I opened the blinds and saw one goldfish floating and I was sad but not really upset because it was an older fish and they do die at time. I want out to remove the body and became very upset when I saw every one of my fish floating with a few on top of the lily pads.
They had no marks on their bodies, they were not twisted or bent (so not electrocuted), and they did not have their mouth as if trying to get more oxygen – so what killed them?
The waterfall was running so the water should have had plenty of oxygen and the filter is working. They were fine before the thunderstorm and they were all still inside the pond.
Lack of oxygen is the usual reason for a massive fish kill and I am not ruling that out completely because conditions were ripe for trouble. Dry hot spell leading to high water temperatures followed by intense rain can cause the top water which is oxygen filled to go to the bottom of the pond and thus pushing the low oxygen water to the top resulting in a quick fish kill.
Also the water-lily is covering almost all of the surface area which could have inferred with the fish being able to get enough air and there were many yucca blossom that had fallen into the pond during the storm which were beginning to rot quickly also using up oxygen.
I also can not rule out predictors. I have killed many raccoons in the past month that have been causing trouble and I saw a cat trying to bat one of the fish the other day. Cats usually do not eat the fish but they will play with them and since two of the fish were found on top of a Lilly pad close to the edge of the pond it makes me wonder.
Other common causes for a fish kill are: poor water quality which I ruled out since this is an established pond and has bio filter; chlorine and chloramine from tap water is ruled out because I used well water; fish jumping is ruled out since all the fish were found inside the pond; the last cause is disease and infection. This is the hard part because the fish showed no symptoms the night before but some infections are fast acting so I guess that is always a possibly.
The plants and frogs seem to be doing okay so I will wait a while before adding any new fish. I have not had to add any fish since I started the pond almost 20 years ago so this was a shock.
The rest of the day was better but really did not get much finished since we decided to go on a road trip. I love eating at Casa Brava in Bedford so we headed there for dinner.