Californians please do not put red eared sliders, bull frogs, or gambusia (aka mosquitofish) in your pond. They are _not_ California pond critters. The first two will eat the native chorus frogs and ducklings. gambusia will eat the chorus frog tadpoles, dragonfly larvae, damselfly larvae, and pretty much everything that really does eat mosquito larvae.
gambusia are simply not appropriate for a pond. And I just had a client who put a few in and now wants to catch them and remove them all because they are harassing the Goldfish and Koi and making them hide. It has been night and day since she put the mosquitofish in. Previously the koi were always out, friendly, and eating well. Now they are hiding and not even coming out for food.