Hi Tim, I just caught up with this thread going back to the 8th of Aug. See
my guesses below:

On 14 Aug 2003 14:46:44 -0700, (Timothy Tom) wrote:
TEST RESULTS of Deadly Pond Water:

O.K. I tested the pond water which killed a goldfish within two hours.
Please note that this water has been sitting there for over 48 hours,
so it is not exactly the same water that killed the fish.

The pH measured at 7.7 using Tetra test kit, the nitrate measured at
perhaps 1 PPM (color between zero and the 2 PPM color on the color
scale) using Salifert test kit, the total ammonia measured at between
.25 and .5 PPM using a Tetra test kit.

Nitrate is definitely not the problem. Since your test measures from 1 to 2
ppm I'm sure it is nitrate and not the nitrite test which measure in 0.00.
A nitrite number would be nice. With no fish for 48 hrs and a reading of
ammonia either means you have chloramines that you're not detoxing with the
right product and after 48 hours those number are lower than what they
originally were when first filled and treated with just a dechlorinator. If
you don't have chloramines in your water system, then I'd definitely say
that leak you've found, is adding fertilizer and who knows what.

Last year there was a mystery fish kill of a pond that a vendor ran a story
on. Turned out it was the feather rock in the pond, all these fine
microscopic glass particles coming off the rock and ripping the fishes'
gills up. ~ jan

See my ponds and filter design:
http://users.owt.com/jjspond/

~Keep 'em Wet!~
Tri-Cities WA Zone 7a
To e-mail see website