Brettski,
I judge by the size at which they sprout legs.
BF tadpoles soon become nickel sized, then quarter sized in no time flat with no legs showing. If they are nickel or dime sized with legs appearing already, they are wood, leopard, or other species. If they are well smaller than a dime and have legs showing, they are toads or tree frogs. Toad tadpoles are very dark with faint gold markings.
Not to worry about gazillions of them. The huge quantities of small frogs attract birds, and they pig out on them.
