## Very likely. There are other things that dissolve in pond water over
time besides Nitrates etc. How large is your pond and how many fish are in
it. What is the PH?

Here is my water:

Ammonia: 0 (as far as I can tell, the dip stick does not change color
and has no green in it)
Nitrites: 0.25
Nitrates: 20
GH: 300
KH: 120
pH: ~8

Pond is 120 gallons, 3 2" goldfish in it. It's been up about 2 weeks
now, this is the second fish loss. The first one had no obvious signs
of disease like this one did.

He died overnight, I think we got the meds on him too late, thanks to
our new pond algae bloom we didn't notice something was wrong for a
while I guess. He was in pretty bad shape by the time we fished him
out.

What should I do? Drain the pond and refill? Half water change? Pull
the other fish out and give them pre-emptive drugs? Leave the fish in
and keep an eye on them?