Razzo, I love those fish! MsJ has the best nerites. I have zebras, spotted, and extra cool spikey in different tanks - all from her.
A couple of things to also try is if you use carbon, remove it.
for some people like myself, carbon enhances the the ability of the diatoms to increase by removing other impurities that might otherwise aid to keep it in check.
The second thing to try is a phos remover pad in your filter system.
Personally, I like the natural method (snails) the best.