In article ,
"Pat" wrote:

New concrete turns the water alkaline. Let it age before use. Or roll on a
coat of asphalt emulsion.

Asphalt emulsion is can suffocate fish until it completely cures.

The MSDS for asphalt emulsion is at:
http://www.neyra.com/MSDSjena.htm

It says:
When spilled in waters containing fish, material will suffocate
fish until it settles on bottom.

Most fish hatchery ponds are lined with hot-mix asphalt. Then this is
sealed with asphalt emulsion because a bacteria detrimental to fish life
can find a habitat in the surface voids of the hot-mix asphalt. The
Asphalt Institutes specifies using a CSS-1 or a CS-1h asphalt emulsion.

http://www.asphaltinstitute.org/Uplo...s_Lined_With_A
sphalt.pdf
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18,000 gallon (17'x 47'x 2-4') lily pond garden in Zone 6
Cheers, Steve Henning in Reading, PA USA