I had to remove the reptile waterfall from the tank. It was trouble for two reasons:

1) It is a death trap for fast growing animals. Tadpoles go into the intake holes, eat on the filter, and grow until they can no longer get back out.
2) It's a snail haven.

Fortunately, I caught it early and most of the tadpoles that had been captured by this thing were still alive and doing well. I believe I saw three dead and maybe twenty live. The bigger they are, the more likely they are to survive stuff like this, it seems.

I noticed the problem because the pump inside of the waterfall started sucking air. So many critters had gotten into it, that it's filter was no longer working well.

The remaining water intake is covered in plenty of filter media material, so the water flow is very slow and will not disturb even the smallest of critters. Also this intake serves as a prime feeding ground.

All of the tadpoles are in 24-7 eat/poop mode. The biggest are about 25mm long now. like a flattened grayish jellybean with a tail.