If you want your tadpoles to grow fast, I suggest putting them in no more than three, maybe four inces of distilled water (to distill the water, just but tap water in the tank a day before you put the tadpoles in). Bank up gravel or sand at one corner of the tank so that the frog will able to climb out of the water when it metamorphoses. You don't need more than a centimeter of the gravel to stick out of the water.
I use boiled spinich as a food supply, but gold fish food works fine as long as you get it to sink to the bottom of the tank. One set back to either of these foods is that it mucks up the water. You should replace the water once that happens. If slimy bubbles or film begin to show on the surface, replace the water immediatly.
The type of frog you want to get might depend on how long you wish for them to remain tadpoles. Some, like the bull frog, take around 2 or 3 years to turn into frogs, while wood frogs only take 3 months at the most. The higher the tempurature and dimmer the lighting, the faster they will grow legs. But, if the water is two hot, they will end up with deformities that could be life threatening. Sorry, but i do not know the recomended temp, just use your jugment, room tempurature sould be fine.
In the wild, more than 99.99% of the tadpoles never make it to the land without being eaten or killed by desease or malnutrition. In captivity, usually 4/5 of the tadpoles die after hatching. So if you plan on gathering eggs from the wild, take one group of eggs, that could mean up to 1000+ eggs. Many won't even hatch an most won't ever leave the water. When they do turn into frogs, just release as many as you don't want and keep the rest. You don't want to overpopulate your tank. The eggs should be in a ten gallon tank filled to the top with distilled water and the tadpoles should be raised no more than 40 to a ten gallon tank with three inches of water. If you don't have ten gallon tanks, then you will need to adjust those numbers to accomodate for what you do have.
If you are getting the little guys from a petstore or some other place, they will give you the kind of tadpole that would be best for what you have to work with.
One rule of thumb that I have learned is if you can see through the tadpoles belly and see it's intestine, then it is a species that takes a shorter time to metamorphose into frogs. If you can't see through, then it could be a bull frog or green frog, which take years to metamorphose. American toad tadpoles are all black and pretty small. They don't take long to emerge to land. Your best bet at finding woodfrogs, which are what i have had the best experience with, is to get the eggs early spring. They are one of the first species to lay there eggs.
A good site for identification of tadpoles is
http://www.pwrc.usgs.gov/tadpole/ one of the authors of the site, Ronald Altig, also has published numerous books and articles about tadpoles and is worth looking into as a source.
I think that about covers it. Sorry if this is too long, but I'm a bit enthusiastic when it come to tadpoles.
