Hi Sarah.
Nobody can give you an authoritative answer on that, so ultimately it's your call to make. Certainly cases can be made for feeding or
not feeding amphibians to amphibians.
As you say, newts feed on tadpoles in the wild, and seem to relish them. So one could argue that anything a newt eats in the wild is fair game.
But on the other hand, I think most caudate hobbyists would probably not consider it ethical (going by the standards of the hobby at least) to feed the larvae of one species of newt to other newt species, for example, which is probably why nobody has yet coined the expression "feeder larvae" yet
By extension, many would probably not feed their newts tadpoles either on the similar grounds.
Having said that though, it occurs to me that tropical fish enthusiasts regularly feed goldfish and other "feeder fish" to their arowanas and other large, carnivorous fish, seemingly without sensing any ethnical dilemma. And I was recently shocked to witness people catching geckos from the wild to feed to their snakes...
Still, there might be other reasons for not feeding tadpoles to newts. For example, it might be the case that tadpoles of some exotic species of frogs that aren't part of the natural diet of the newts in question might not be healthy for them to eat. Cane toad larvae being fed to axoltls, for instance, might not be a wise idea. Also, it depends on the status in the wild of the frog species in question (is it endangered?) and where you're collecting from (is it legal?).
I once fed a few tadpoles of a common species to my newts, and by all appearances they loved the treat. But I felt immediately guilty and won't be doing it again
All things considered, one could ask: it is really necessary?
<font size="-2">(by the way, we do have a section that deals exclusively with food, so I'll be moving your post there once I see you've noticed this)
</font>
(Message edited by TJ on March 23, 2006)