Originally posted by aivlas
It can't really seeing as it would of killed all animals in the area, I will say that co2 escaping from a lake or river would probably kill the fish.

I would draw that out because of one reason. If CO2 would come from underground, at least few people would be sick or dead already because of it at the surrounding area. That's not happened. A place which is holding 100,000 fish, it's huge. It would have some impact on the local population if it's CO2.