Bad vinegar eels ?!

This is not entirely new to me, but the only experience similar that I heared of before referred to vinegar eels not purified carefully.

Living in vinegar, these organisms must be harvested for feeding fish by the one or other method in order to prevent vinegar from infesting the aquarium. Normally, this is no problem at all. But I have heared of one case where a considerable amount of vinegar entered the tank water and the fish died because of a substantial change of their environmental parameters.

But this is nothing to be alarmed about normally; it’s quite clear. That the vinegar eels should not be fed to the fish with a considerable amount of the vinegar is self-evident. Every method for raising vinegar-eels contains a method of harvesting them and does not include to add them together with their vinegar to the fish-tank.

Therefore I am sure that you did not do this either. I only reported about that mistake as having heared once; there is not big mistake that is never made by someone. But not in this case, of course. And therefore I am puzzled as others are by your bad experience. What could be the cause of it? I assert to your opinin that – normally – it can’t be coincidence.

Your method of harvesting the eels is mine too; I agree with you: That cannot be causal for your desaster.
I have no other theory than you have: There must have been some toxic pollution within that culture.
But what and how and why?