I have thousands of toad tadpoles in my koi pond right now, do every year. I could close my eyes and make one swipe with a 6inch aquarium net and get 100 tadpoles. Wouldn't blink about using 100 to feed if I needed to, or worry about the inviromental impact since it's my manmad pond in my yard, usually worms or fish starts up babie garters just fine.