they cant eat what the other fish are because they're quarantined in a breeder box lol.
if they're just by themselves in a box u could reduce their stress and make them feel a little more comfortable by adding some plants. I have RCS also and they breed regularly. They seem to enjoy to cling onto the floating hornwort that i have, but i'm sure that any plant will do. As far as food they wont need much of it so dont overfeed! unless they are smaller wafters i'd say maybe half a wafer for 15 shrimp is plenty, so it mainly depends on how many u have i guess?
& while they may primarily be herbivores these shrimp are actually omnivores, they will eat meat foods too. Mine will skim the surface of the water everytime i feed bloodworms, grab one and sink to the bottom while they much on it.
If you ever have babies in the future u shouldnt really need to worry about what to feed them for as long as you keep them in a planted tank there will be micro-foods from those plants for them to eat. Another note on breeding, if you do wish to breed (i suggest it as i dont see too many
LFS carrying these shrimp! i dont know why theyre beautiful) you should keep them in a planted tank specifically for shrimp. I have a 10 gal. tank just for my ghost shrimp and RCS. You can cover the filter intake with some panthose and a rubberband to keep the newborns from being sucked up, and this also accumulates the small debris floating throughout that the babies will soon realize build up on the intake, and they'll gather there to feed.