I know the experts are going to come. But I can say from experience with a small garden pond that yes, at some level, you will stress the fish. I walked away once with the hose in the pond. Forgot about it. came back to stressed fish. So I know it can happen, what you need to know though, is just how much is too much...This I can not help ya with. Or perhaps there is a way to neutralize the water on a large scale such as yours? This would be good info. too.