Be cautious of putting fish in a new pool liner intended for use as a swimming pool. Some liners are impregnated with algaecide chemicals to help prevent algae growing on the liner. This makes it toxic to fish. We had a bunch of goldfish and a few koi thriving in a pool with a torn liner half full of pea green water for several years. We had a new liner installed and in two weeks almost all the fish died because the liner was intended for a swimming pool, not a fish pond. After a few months the chemical in the liner wore off and now we have no problems. I'd put in a couple goldfish at first to see if they survive before stocking fish you want to keep.