Feeding tadpoles

I have a very small pond in on my allotment which has about 40-50 tadpoles in it. As it is constructed with pond liner and they are getting through the pond weed at an alarming rate, I'm wondering if I should feed them regularly as there's not much mud to forage in  I have tried flaked fish food which seems to disappear and cucumber which they swarm over. I read that there comes a point when they like a little meat - it seems a bit unkind to put in worms, slugs and snails that don't naturally find there way in to the pond - so is meat essential to tadpole's development or can they survive as veggies?