Koi-lo wrote:

snip

You may want to check the PH and Nitrate levels for a start. Is there a
lot of rotting leaves and other debris on the pond bottom?

snip
OK, did what water tests I could. My test strips for Nitrate must have
been contaminated so I couldn't test that yesterday. PH is higher than
normal, a little above 7.8. Typically it runs 7.4 or something like
that and had been very stable all summer. No ammonia. Hardness and
Alkalinity are both up a little as well (I forget the exact numbers but
they are in normal range.). Water temp is 56 F. 700+ US gallons.
The veggie filter is a little messy, but nothing horrible I don't think.

PH in QT tank is WAY off! Very low. I'm trying to rectify that right
now. Ammonia was a little high. I had been doing a better job of
keeping it stable but have been sick lately.

I've unplugged the heater in the QT tank and will allow the water temps
to get closer. It's warm here again (North Alabama) so it may take a
while. Either I couldn't see before or the sick fish has moved his
fungus. It's an oranda of some sort. Smaller fungus patches now around
his head only.

Funny thing about the fish that lost his scales. Even his fins have
changed color. The dorsal, caudal and anal fins are all black now.