TJ, last summer when we had an abundance of leopard frog tadpoles in our pond-in-the-works my son and his friends insisted on bringing a lot home with them. I'm talking probably around 2000 of these little guys. I have a 150 gallon aquarium that I have LMB, BH, CC, gar, etc. in. Each species in the tank LOVED eating those tadpoles. Not sure if that's the same scenario you're looking for, but in my experience, in a very captive environment, they slurped up the tadpoles and couldn't get enough. Not sure what to think of your experience except that maybe you've spoiled your babies.
