Tadpoles in our pond
You question is somewhat out of the expertise of Master Gardeners. I suggest you check in on forums about ponds and pond wildlife.
That said, it is my understanding that it is not unusual for there to be a large number of tadpoles in the spring and that this population thins out naturally due to predation and competition. Very few of them become frogs. If you have fish in your pond, the large tadpole population probably makes them quite happy. Read here: