Hope it's not too late. I raised a bunch of tadpoles feeding them various fish food and slightly boiled lettuce. They loved gold fish flakes for sure. I also tried some other fish foods. They have tadpole pellets in pet stores, but they're kinda expensive if you raise a lot of them. Flakes and lettuce worked best. The main thing is to make sure that you have PLENTY of water, and it's not clorinated (clorin will killl them). Boil or let it sit for 24 or better 48 hours in open container. Depending on the number of tadpoles you have... The best thing would be about a quart per 2 of them. Whatever fish food you put in must be eaten within next 3-4 hours (lettuce can stay a few days). I fed mine twice a day. When they first hatch, they eat very little. So it's trial method - to see how much they'll consume. I had large tanks (the biggest plastic boxes I could find, from the nearest store) and did not change water, just added it as it evaporated. I was also lucky, mine hatched in summer and I had a few tanks covered with algae, which tadpoles happily scraped on.
If tanks are too densly populated, you'll see some tadpoles accelerating their growth and some falling rapidly behind (it usually happens anyway in captivity), dense population also increases mortality, so the less tadpoles you have per tank and more water they have per capita - the better. UV exposure is also important. They have Repti-light or smth. like that in pet stores. It's quite a chore altogether.
The main fun begins when they turn into toadlets - you'll need very small insects. With firebelly toads you would probably have to get fruit flies, or new-born crickets or very-very small roaches. Fruit flies and probably crickets can be ordered online. If you want to be prepared in the future, you could get Turkish (or Turkistan) roaches and breed them. They don't climb out of plastic containers, easy to breed, but no matter how careful you are some escape when you take them out and make home in your house.
My frogs are fairly large species, so I just ordered medium-size crickets by the thousand... My first year out of about 60 tadpoles that I kept 29 became frogs and grew.
When they grow the hind legs, you need to start preparing something for them to climb on. The tail resobtion happens fairly rapidly and if a new froglet does not have a place to sit on, he will just drown. I used cedar boards placed at an angle. Wouldn't hurt to presoak them separately for a week or so if they're fresh.