Many of the creeks around here have Gambusia, Black Strip Top Minnows, Red Horse Minnows, and others.
I had tried to start my pond off the right way as well, but unfortunately I did not check it one last time before stocking it, and it has a nice population of Green Sunfish.
I am now in the process of trying to thin them out which has been fun.
As many has mentioned buy from a trusted source.
