You need to take a long, hard look at why you're keeping fish and evaluate wether or not it's the right hobby for you. Fish are fish, not garbage disposals for small animals. You should build your fishkeeping practices on what's best and what's most ethical for fish... pets or feeders. I never use live feeders unless it's necessary, other than the occasional worm for my Pike... you'll never see me tossing random small fish and animals in front of my Pike or my reptiles just to see what animals they can make disappear. If this is your idea of fishkeeping, then you are in the wrong hobby. That kind of bone-headedness is not what exotic animal keepers need to be represented by in these times of legislations and animal bans, and it's not the kind of thing to progress this hobby in any way. You seem young... I'm guessing 12-14... and I can understand that kind of desire, but I hope that very soon, you grow up and realize that you arent a fishkeeper when your idea of fishkeeping is owning small animal disposals. You might keep fish, but until you realize that... you'll never be a fishkeeper.
As far as Tadpoles specifically, a lot of Frog species are threatened or endangered, or at least protected. If you start collecting Amphibians and feeding them to your fish, then I sincerely hope one of the resident DEC agents finds you and hits you with a hefty fine... not to mention it's wasteful of a very important species in the ecosystem. And did we mention that some Frog and Toad species are highly toxic? And they are bottom-dwellers, sifting through the mud for small inverts, often in stagnant water, so the risk of parasite load is heightened by using them as feeders. Stick to pellets and varied frozen food... Cichlids grow big, happy, and healthy on them.