Hi Will,

You mentioned you had fish till a heron took them, and you're planning to
add more. You might want to check your pH & KH and see just what your water
chemistry is now. Over time a pond changes, and your fish may have
gradually gotten use to it, but new fish might be put into shock.

Most of us take 10-20% old water out and add fresh in as often as once/week
for good fish health. ~ jan
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Zone 7a, SE Washington State
Ponds: www.jjspond.us