Ive reared a couple types of tadpoles before and found that they are not picky eaters, boiled letuce, fish flakes, newt bites, shrimp pellets, algae disks, and then they eat eachother if they die.
The higher your water temp the faster their metabolism and more they need to eat, therefore they turn to frogs faster, but don't try to speed up the process because they get deformed (like quick growing farm chicken feet do) if they grow too fast.
I also noticed that you need to do water changes a little more frequently than fish but BEWARE when you replace the water you took out do it SLOW. For instance if it was a 10 g and you removed 2 gal let it take you an hour to replace all 2 gal. Ive killed the whole stock by doing quick water changes, and more than once so go slow. (They can live in some pretty bad water but they cant handle a quick change in water chemistry)
But im intrested too, what state do they come from, what type of ecosystem was it (woods,swamp, field) lets figure out what you got.
If you found them in a small container that rules out Bull frogs and Green frogs because they only lay in permement sp? water (unless some one put them in that container, they probably did) but other frogs are known to lay their eggs in temperary spring pools where its a race for the tads to grow b4 the pool dries.