springtails are used to supplement normal feeding with flies/pinheads/roach nymphs etc. I don't know of anybody using them as a staple. In very large enclosures it is possible to have enough micro fauna to sustain the frogs for long term, but in smaller tanks and not being fed anything else a population of frogs will quickly decimate a population of springtails. It is also exceedingly hard to supplement vitamins/calcium with springs