Lucille, take a look at the sealer linked below.
There are other types available. Google, "Concrete pond sealers".
"Horton"

Here is a link that might be useful: Conctrete pond sealer information.

Lucille, I'm going to guess that since you're in Fresno, you don't get hard freezes. So you could use the same thing we use in South Florida.
Almost everyone around here uses Thoroseal, and you can get it at a HomeDepot or Lowes.
I used it when our pond was new and it's held up perfect for over 15 years now. Mixed some black cement dye in it when I did it.
Corrie