This will probably be the only fish to ever be featured here, as we obviously do not have a natural water source in our typical urban yard. Although it looks much like a guppy, the mosquitofish (Gambusia affinis) is a much hardier native species. It lives in many of the streams around here, as well as in any ponds where it has been introduced, ours included. As can be deduced from the common name, these fish are great for controlling mosquitoes. They are also capable of surviving in very small ponds, even when the water freezes over sometimes in the winter.
Mosquitofish are live-bearers, which means they do not lay eggs but give birth to fully formed young. This is one more reason for their success in almost any environment, as the tiny fish can immediately escape predators and start their search for food. They are also top-feeders; you can see in the photo how the mouth is located to open at the highest point of the head rather than towards the bottom. These fish are very good at grabbing anything edible on the surface of the water.
Although we don't have to feed our fish, I sometimes keep a bucket of water for several days until it has mosquito larvae in it. Then I dump the water into the pond. One other way I feed our fish is to use an electric mosquito zapper (looks like a small tennis racket). During the summer, mosquitoes will swarm to my legs when I stand by the pond, so I just wave the zapper over the water and fried mossies fall in. The fish are quick to learn this each season and respond by enthusiastically gathering at the water's surface.