I'm in the Chicago area - we know harsh winters. Bog plants (that are hardy to your zone) can be planted in the bog and left there. How are you removing them from your bog? Digging them up?
How is the bog water no longer entering the pond? I'm assuming you mean all the "bad" water has now been recirculated, but maybe I"m missing something.
The bog overflows into the stream that leads to the pond. I have a dedicated water supply to the bottom of the bog. When I turn off that supply line, the bog no longer overflows into the stream.
We dug up the plants - Cannas, papyrus, that kind of thing. Probably not hardy for Salt Lake City.
We are changing out more water and I turned up the flow of the stream to get more circulation and aeration. Should I rinse my filter pads to help get rid of whatever came from the bog and is harming the fish?
I don't know if it is a related issue, but we were having a big algae bloom - pea soup, before the bog incident occurred.
Thanks!