Ccoombs1 is correct about ProformC to some extent in that below 60 it will go to the bottom of the pond and the level becomes too high and poison the fish but if the bottom and top water is being mixed all the time it is not a problem. Volume for the ProformC needs to be somewhat close with in about 10%. The prazi can be off even more and demilin can off even further. You have far more leeway with these than other treatments. I don't think that it is HS or CO2 from decaying matter as not all the fish died at one time which is what I would expect with either of those. It would be possible that the levels could maintain right at the level to start to affect fish for a period of time but if that was the case than when winter hit and the pond froze over the levels should have increased to the point to kill all the fish. But it could be one of those poisons but not very likely. If I had to guess I would believe costia only because of the effects in cold water but it could another parasite that has weaken the fish to the point that the winter is finishing them off. Mike

Along with Cindy's information, and since the water chemistry checked out okay. If your fish were breeding the Shubunkin could have been a female that was run ragged by the males chasing her and she just pegged out. Some fish die sooner than others, just like people! You have enough room in the pond [558 US gallons approx,or 464 Imperial gallons] for the number of fish you have. "Horton"

Yay, thanks, Kimmsr and Rhizo 1!! I am relieved! I've been trying to think what I did differently this year to get worms in the pile for the first time, and I think it must be the handfuls of old leaves I put in. I read up here yesterday about worms, and seems they like to live under leaves and lay their eggs there. Ashita

Egbert, what are the test results? What is the water temperature? Is the tank heated? What size tank? Filtered or non-filtered? What type of ammonia test do you have? Is the test a dip strip or a reagent type? If reagent 1 or 2 bottles of test solution? Ammonia tests ( strip or 1 part reagent) can be skewed by water conditioners. This time of year is usually when people that have had bettas start getting sick or lathargic. The temps start to drop as the days get shorter. Betta's need heat, they are indeed tropical fish. Room temp. can be 5-10 degrees warmer then tank water temp. Think about a glass of water, in the winter I have one on the nightstand because the heat makes it dry. The room is comfortable but the water is still cool. I would suspect it is a temperature issue, but answer as many of the ???s as you can to give more info for a better resolution. Good Luck.