Snails will eat anything they can get their mouths on from detritus, to slow moving amphibians. While I would not worry too much about the snails and your tadpoles, I personally detest live snails in my tanks.
Daphnia are filter feeders that eat microscopic plankton and are no threat to anything larger than bacteria and protists.
I think snails can only dangerous for the first four days after hatching when the tadpoles are hanging around the whole tank like commatas or semicolons. Although it's related to the snail species.
My axie is acting woerd he was a rescue as stated in a different post he got better and now seems to be deteriorating again...again all tank conditions are OK and as should be. He seems to have some black dapple like pattern under his bottom lip? Is that normal? And his two back feet have a little wierd growth? Almost? Tiny tiny tiny lump. His capillaries in his feathers also appear darker and more visible. Any help would be appreciated