Ponds, fountains, duck ponds, pond supply stores, etc. Any frog that would grow to be 6 inches will need a large territory, a big tank. Or you could do what I did and raise them until they hopped out of the water and where able to turn into a tiny adult frog and let them go where you found them. As long as the tadpole is native and they have not been sick at all, I would think it would be fine.