Back in the late 70's I used to dig a hole in the ground large enough to keep a 10 gallon tank in it. I would fill it with water and let nature take it's course. Basically the mosquitos. I would collect the larvae with a fine net every day, put them in a little clean water then freeze them. When I needed to feed it to the fish, I would thaw some out in the tanks. It worked quite well and I didn't have to worry about having them develop into flying insects. The fish didn't seem to mind if they were frozen. Just my 2 cents worth. Kaycy