Tadpoles are voracious meat eaters. Shove a bit in and you'll see. :)
25 years ago I found some bullfrog tadpoles in a garden centre. Since this thread is here I'll share the story via the poem I wrote about it.
Quite a few came into the country then. We made sure they didn't escape into the...
Take out most of the green gloop, put the tadpoles back, add pond weed. Weed creates oxygen, they need that, plus they eat a small amount of green gloop and the weed. When much bigger (May/June) they love tiny bits of meat/bacon occasionally. Make sure the pond is well oxygenated generally.