 In fact , tadpoles developing in ponds and streams are typically herbivorous . Pond tadpoles tend to have deep bodies , large caudal fins and small mouths ; they swim in the quiet waters feeding on growing or loose fragments of vegetation . Stream dwellers mostly have larger mouths , shallow bodies and caudal fins ; they attach themselves to plants and stones and feed on the surface films of algae and bacteria . They also feed on diatoms , filtered from the water through the gills , and stir up the sediment at bottom of the pond , ingesting edible fragments . They have a relatively long , spiral @-@ shaped gut to enable them to digest this diet . Some species are carnivorous at the tadpole stage , eating insects , smaller tadpoles and fish . Young of the Cuban tree frog ( Osteopilus septentrionalis ) can occasionally be cannibalistic , the younger tadpoles attacking a larger , more developed tadpole when it is undergoing metamorphosis . 
