Ok guys I made the mistake of asking the question at John's Viv built article where he actually asked me to start a new thread, so here it is.
We see that most people have included Sringtails in their vivs and that people say vivs are a self sustaining, almost natural system, thus,
1. Why not include earthworms as well?
a. Do they pose some threat / danger to the frogs in some or another way?
b. Would they perhaps damage the plants?
c. Would smaller worms not be eaten by the frogs as I'm sure they do eat worms in the wild?
d. I have read that ants may be the factor to re-introduce the poison in the frogs' skins, surely earthworms would not do the same?
e. Or would earthworms make live so much harder for the Springtails as they feed on more or less the same things; detritus and dead plant material.
I'll leave it to the experts to clarify this.