What about ROCKS

HI,
Completely new to the back yard pond hobby, but can't wait to jump in and get my feet wet.
We are starting to dig, but I just found out that we shouldn't use limestone rocks if we plan on having fish, is this true?
If so, what does limestone do to fish? PH, Alk? All of my bordering rock walls are limestone, but I could get the field rocks for the pond if I had to. And keep the pond about 4-5 away from the pond, is that far enough for runoff?
I hope so.
Also, the pond is going to be 15' x 20' with about 2.5' deep, with a waterfall,
any suggestions on pumps, filters, skimmers, etc.
Thanks!

cr8signs

You will find both pros and cons with using rocks. Myself, I have very few in my pond and many around it.

I would have to do some research before advising you on limestone. I personally don't think runoff should be a problem because you don't want any runoff into your pond. All rainwater that doesn't fall directly into the pond should be shed away from it.