Tadpoles eat water boatmen and visa versa, this balances the eco system in a pond. After losing my last two twenty year old Koi to a fox I decided not to restock, the tadpole population last year was phenomenal, we had to brush the thumbnail sized frogs off the lawn before we mowed it, everytime I weeded the garden the froglets would be jumping around. This year is no exception. I love frogs but draw the line at them jumping on my hands. My frogs are also averse to eating slugs and snails as I am inundated with the b------rs. Next year I shall be taking a few bucketfuls of frogspawn to the local canal as my garden is overrun.