Gambusia affinis are great for your pond, they eat all the mosquito larvae, one fish can eat up to 100 larvae a day---warm water fish, but they always make it thru the winter in my pond. I thought I caught them all actually but I guess I didn't---the other day I went outside and seriously there were about 30 of them "sunbathing" in the warmth on top of the cinder block.
I didn't have my camera with me, but when I just went out I caught some on top of there again.
And don't mind the pond, it's starting it's lovely
spring green algae bloom color.
BTW, these fish have live babies....lots and lots of live babies. I started with 7 about 3 years ago that I paid $20 for on Ebay(lots of government agencies give them out for free)......last summer I had probably several hundred at least. I gave some away to local ponders. They live 2-3 years and have up to 3-4 broods of fish a year. And the female is usually larger and fatter than the males, making them easy to ID.