I was worried wild mosquito larvae might be risky, but perhaps I'll give them a try with my gouramis. I had a small wild fish once which I fed up with them before setting it free again. Boy, did that fish love mosquito larvae!
Fun tip... if they’re in cold water they’ll go into shock when you drop them into a tropical tank. If you’re feeding a lot of them, float them first to raise the temperature. Then they’ll be active in the tank until they’re caught, giving the fish even more fun.