Thanks, I'm open to any advice or suggestions.

I forgot to mention that I did have (and still do have) aeration in
the pond for the winter. Whenever I shut down the bead filter for the
winter, I put air stones in the pond to keep two holes open for
gasses. They keep two 1.5' holes open in the ice throughout the
winter. I put one set of air stones near a more shallow planting area
where frogs tend to hang out, and then dropped another down near where
the fish overwinter at the bottom. (There's a big boulder down there
resting two smaller stones, making a cave.) The aeration is still
running--I haven't started up the bead filter yet and that's when I
usually pull out the airstones. I want to do some clean up before I
start up the bead filter but I hope to get to it soon.

The other thing is that my estimate of 100 fish is probably a bit
high. I'd say there are definitely 70 and could be as many as 100, but
that's probably a stretch. They don't stand still for a head count so
I'm not sure. The average fish size is probably 5" + tail size, and
some of the tails are quite long. The oldest fish are more like 8-9" +
tail but there are probably around 6 of those.

I looked today and I did notice one fish with some lumps on its side
and one on its head. I'm not sure if that's related or not, since all
of the fish that have died didn't have any visible ailments. This one
didn't come close enough for me to net it for a closer exam. (Smart
fish.)

Thanks for any advice. If there are any questions I can answer, please
ask.

Dave