How do tadpoles get in the pool?

You can always buy tadpoles and a pet store, and put them in your pond. I am sure that it will also happen naturally.

"Build a pond and they will come," or something like that. If there are frogs in your neighborhood they will find your pond.

I would suggest, though, that you do not turn tadpoles that you bought in a pet store loose in your pond. When they turn into frogs they may become an "invasive species" and upset the balance of your eco-system. Some frogs eat other frogs and even birds. (www.rosepond.com)