[Roy hit the nail on the head, large fish dying first, usually means low
O2.

I would recommend those who live in areas of much rainfall have the
test to
measure KH. Rain water has no buffering, and supplemental treatments
need
to be added unless other means are in the ponds.

Okay, help me out RPers, was it limestone or crush oyster shells that
was
recommended as a slower method than baking soda to increase buffering?
~ jan


~Power to the Porg, Flow On!~

Most tap water (at least here in the US) has calcium carbonate wich will
buffer your water. I doubt it was a PH crash. I agree that low O2 is
the most likely culprit, fish deaths from low O2 usually occur early in
the morning- before the sun is up.


--
Koitoy