@Great Argus I was wondering if it was a Cane Toad tadpole. I was going to rescue them from my dam as the water levels are receding and raise them to adults if they were Tree Frog Tadpoles.
@Jake - you could rear them and if they turn into Cane Toadlets (it will be obvious as soon as they near metamorphosis) put them in the freezer. And if they are not Cane Toads, release them.
Tail-length is a key identification for them (along with colouration etc - e.g. toad tadpoles are always black whereas frog tadpoles are at most dark brown). In toad tadpoles the tail is only one to one-and-a-half body-length. Native tadpoles have much longer tails.
Also, in case you don't know this, toads lay eggs in strings and frogs in clusters (like jelly). If there are any eggs still there you will see that.