I want to build a little pond for the frog in my backyard, but I don't want to spend to much time and effort maintaining it and I dont want to run a pump or filter in it. So if I put some little fish in there will they eat the mossies and pollution? How can I keep it clean?

It will be a pond that will naturally dry up sometimes and wont always be full of water.
Sorry, I mean. if it can be a pond that will dry up sometimes, will that help to keep pollution and mossies out?