It's been very hot here. I suspect low oxygen and hot water. I bought a swing arm patio umbrella to put over one edge of my pond for shade, even though I have plants. My pond is only 2/12 - 3 feet deep, so a few days of high temps in a row can really change the conditions.
There are also viruses that lay low during the cold weather and pop up once the water warms.
There are a few varieties of toad that have a toxin on their skin. I only had problems one time , in my smaller 4x6 with toads. I found 15 mating pairs at the same time. The water was horrible, and the protein bubbles on the surface made a coating that was a bit choking for the fish. I had thousands of long strands of eggs in the pump. (Toads lay long strands, frogs lay floating eggs) I don't have a skimmer on that little pond, so I flooded it a few inches to get rid of the foam, and cleaned the pump out.
I appreciate all the kind words and help. One thing for sure, now my ponds are only for plants, frogs, toads, tadpoles and snakes--no more fish. The fish I had were just comet goldfish, but I have had them for years and a few were almost 1 foot long. I had about 100 mosquito fish--now I'll have to go purchase some dunks...oh well.
Sorry to hear of your loss :( This was a horrible winter here in Michigan also! I lost all my Koi fish :( I mean every one, I had about 12 large ones too :( altogether over 87 were caught in the ice :( The huge pond was frozen over, we made many holes in the ice to make sure they had air.. Pond is 18 ft. deep , I believe the ice then turned to slush,they found a way up, then it froze over and they all were caught in between layers :( I am so sad, I really am considering not to buy any more beautiful Koi for the pond ;(
Tootsie, that is terrible. I never would have thought that could happen. You would think they would just stay on the bottom and sleep til the ice was gone, not to up the holes. Did you use an auger to drill them. No, you would have made too much noise. but you must not have use deicers. They make really big ones for huge ponds like yours. 87 fish. My heavens. I have only 17 little fish, mostly gold fish but three koi. I say 15 of them the other day including my biggest who is only 10-12" long I think. Hard to measure a fish you can't catch. lol. I am missing one more. They sleep in caves in the rock of my 3000 gallon pond and sometimes they just never come out in the spring. Again, I am so sorry you lost your lovely fish.
Thank You for the kind words :) I plugged in the movie camera to see all of the Koi that were swimming and jumping over the plastic Aligator, LOL They all were so amusing to watch :) As soon as they would see me coming, they would follow me as I walked around the side of the pond. I used the same container filled with their food :) They were like little kids begging for their treats!! I am glad I took the pictures of them :)
Oh tootsie, you should try again. You obviously get so much pleasure from your fish and have such a great pond. I have felt the same discouragement over the last four years as each spring either none or few of my fish survived. Even if I only had them for a summer I grew very attached. And DH names them all. This year it appears we have finally figured it out, or maybe nature was just being kind. I have a friend whose fish all survived the winter then died in the spring. He suspected some sort of illness. But this year it appears that all of my fish have survived, even the big guy. And we though that the bigger ones could never make it through the winter. And one little koi I bought last year from PetSmart who is really growing. They are really hungry and like yours, once they recover from their long nap, will remember me and follow me around the pond also looking for food. I can certainly imagine your terrible feeling of loss after having your fish for so long; but you shouldn't give up. And if you don't, do try the larger deicers; some float and some can sink to the bottom to create a little warmer spot. Hard to warm up 18,000G of water I would suspect.
dont give up on the fish. im so sorry to hear they passed away. the causes can be too numerous to just guess why. i have a 2250 gallon pond and raise koi and goldfish. from what i read it possiably could have been a PH crash or low dissloved oxygen content. possiably the pond just got too hot. when i first started out i had a massive disease outbreak and a huge fish kill , it heart breaking i know but dont give up.! it can be such a rewarding hobby! perhaps try a liner pond and go a bit deeper with it. EDPM is a good type of liner to try. fish can not tolerate city water and their water MUST be treated with a dechlor agent before the go into the water or it will burn their gills and then they can not breathe, perhaps this was the cause?? did you treat the water? i had to learn all these things the hard way! then i did some research and joined a koi club. i learn something new at every meeting. also did you test your water for nitrate?, amonia?,PH?, nitrite? these are things we have to do. i suspect due to the toads their was also i high concentration of amonia and nitrate in the water and this can be deadly in its self. i try to do about 10 percent water changes weekly for the health of my koi . my goldfish breed a lot and this raises the levels of nitrate an amonia in my water.?? i can only guess but i urge you not to give up on raising your fish! remember water quality is very important when raising fish. we should test the water to see whats happening in our ponds. its all a learning expirence. again im sorry for your losses! dont give up though ! give it another try. learning about ponding is a continous process! i wish you the best and hope ive helped in some small way! :)