A little concrete is not going to hurt the fish. In my case, I used 70# concrete
in a pond of only 300 gallons. I only hose off the dirt once before I filled the
pond and added the fish.

bk wrote:

1200 gallon concrete pond with diamond brite finish. I believe I have a slow
leak where I have a 1.5" pvc pipe cast thru the wall. I used to use this for
plumbing, but now we just run a hose along the pond bottom tot he filter.
I'm sure I could plug it with hydrolic cement, but I don't want to hurt the
fish.
Any suggestions?