For example, do frogs need a shallow area at any stage in their life? I wouldn't be surprised if they can feed better in shallow water. Can you adjust the depth to meet their needs?

If you are interested in enjoying some birds that like water (ducks?) they like water that is shallow enough so that they can get to the plants growing on the bottom. I know they eat the plants and would guess they eat some larval insects that live in shallower water.

I do have a friend who has a shallow pond maybe 15 inches deep and 10'X 10'. Without a great deal of effort it seems to have achieved a balance that allows everything to survive without any pumps or filtration. She lives in Hawaii and her pond has guppies (little fish she put in), frogs (or toads) that arrived on their own and a number of plants. Her pond has been on its own for years.

There is a forum on ponds at Garden Web. I have provided the link to it below.

If you do create a pond from your pool I hope you describe your experience as you gather it! It is such an interesting idea.

One thing I've noticed with my small pond is that as long as the water is kept moving it stays pretty fresh. In spring, as soon as the water thaws, I throw a small pump in just to keep the water moving. In summer I go to a full fitration system. I guess what I am saying is that chances are you could adapt the current pool filtration system or at least some part of it for your needs.

By the way, having fish in your ponds is pretty addictive and they are for the most carefree. If you have mosquitoes in your area the fish will eat the mosquitoe larvae in the water.

good luck with your project,

Glen