IMHO, it's a bad idea. Bullfrog tadpoles are *huge*, require large tanks, eat constantly, can take nearly 2 years to transform, and turn into a giant eating machine that needs an even larger tank (and which cannot be released in many places, due to acting as an invasive pest).
The best thing to do would be to go down to the local pond this spring and catch some tadpoles. Most likely, they'll be a smaller, easier to keep species, and because you know what pond they're from, you can release the frogs.
Oh, and red-leg is a bacterial infection due to contaminated water.
Mokele