Concrete is alkaline by its ingredients. This raises the pH of the pond
water. In a fresh concrete pond, the water get too bitter for fish and
plants. Washing the new concrete pond reduces the bitterness, enough for
the fish and plants to tolerate. A little junk of new concrete does not
affect Water Quality much, since people here have hugh ponds. Also, us
ponders have plenty of plants in our ponds. We have lots of organic
matter in them. This tend to lower the pH. A little fresh junk of
concrete is of little concern to us.

If you put a junk of fresh concrete in a small pond, you need to wash
the concrete with acidic solution first. This would reduce the effect
concrete has on WQ.

G-Hoch wrote:

A couple of years ago I made a base for a water lily spitter out of
quick-crete but I heard that you shouldn't put quik-crete in a pond.
What is the difinitive, once and for all answer to this question. I
say where someone was making an underwater light with quickcrete and
no one questioned.

P.S. How do you spell quikcrete?