Christine_B wrote in
:

What is the best way to go about cleaning up the pond so as
not to cause any further harm to the remaining wildlife?

if you think cement fell into the pond, first thing to do is
take a pH reading. raw cement is very alkaline & a rapid pH
change will kill fish & other wildlife. it won't do any pond
plants any good either.
i suspect that adjusting the pH (slowly!) back to a more
moderate range will solve your problems.

lee
--
Last night while sitting in my chair
I pinged a host that wasn't there
It wasn't there again today
The host resolved to NSA.