Followup UPDATE

The following test was done. One bowl of water from the Auto-refill
system was collected in a plastic bowl, and a second bowl was filled
with tap water from the kitchen faucet. Both bowls were treated with
dechlorinator/conditioner (TetraAqua Aquasafe). Two goldfish per bowl
were acclimated and released into the bowls. It is important to note
that both bowls were kept in the house (Thermostat kept at 79 degrees
during the day, and 84 degrees at night.

RESULTS AFTER APPROXIMATELY 24 HRS.

ALL GOLDFISH ALIVE.

Well this rules out the auto-refill system as the culprit. I did
remeasure the temperature of the pond water and found it to be 85
degrees. We are having a heat wave in South Texas. Could all my
problems be as simply as the pond being too hot? Can 85 degree water
kill goldfish in a couple of hours. I never saw the goldfish gulping
air near the surface as I would expect if the temp were too hot, and
the oxygen level too low in the pond.

My next test will be to go get a couple bags of ice, and lower the
temp of my pond to below 80 degrees and see if the goldfish make it
through a few hours. As I mentioned in my earlier post, the pond did
originally have 3 koi and a catfish in it for nearly two years, and I
believe koi are more heat-tolerant than goldfish. At this point I
have ruled out the following as culprits in killing the pond fish:
1) Municipal water supply (both from auto-refill and kitchen faucet
water supported fish inside my house in a bowl)
2) Electical short-circuit/current leak (Fish died with all electrical
devices unplugged/pond circuit is on GFI circuit, and any leak should
switch the plug off anyway)
3) Rock in pond (Rock removed, and fish still died)
4)Chemicals, contaminants, poisons (After over ten complete water
changes, if the water is still toxic then I have discovered a highly
deadly biotoxin that probably should have killed my whole family by
now.
5) Pond liner (Commercial pre-formed liner in use for over two years.
6) pH, Ammonia (tested and while not great, not likely to be able to
be acutely toxic to fish.

There is not a whole lot else to test now.