I have dwarf barbs in one of my tanks for the exact same reason, unfortunately despite supposedly having some of the smallest mouths they are nimble af and suspiciously this is the only tank in which the shrimp have not taken off. I never caught them in the act, but same with my betta and when they passed (fuck dropsy) the population exploded. Fwiw, in my limited experience the detritus worm and copepod community has always calmed to what I consider an acceptable level with time and without predators, I'm not sure why this is