New home in Catskill region NY 

about 1/4 acre spring fed pond . Beginning of may only newts in the water and a single large koi . Now two weeks later and the pond is alive with many blue gill . Very aggressive , lots of fun to catch . Hoping to stir up some other species like bass , trout . Any ideas on when fish would be active ? This pond has not been fished for a long time . Bluegill are small, maybe over populated ? Would that mean no larger fish ? Want to stock , do you think trout would find their way out thru spillway ? Ive heard spring ponds are colder and trout may be a good option 

thanks for any ideas

Maybe yellow perch, rock bass, and some largemouth bass in the mix.