I have kuhlis and cories in with my RCS. I've seen even baby RCS snatch food from the mouths of the kuhlis, and after countless hours of watching they've never eaten a single one.
In fact, the shrimp are breeding out of control. I'm actually looking for something that might pick off some of the baby shrimp, while hopefully others survive in the moss and lots of plants & cover...
In another tank I had some cardinal tetras and ghost shrimp, but the tetras occasionally harassed the shrimp, especially biting their eyes. Surprising since the tetras never ate food off the bottom, but bit the scavengers sitting on the bottom while they ate the fallen flakes. Even my adult RCS are smaller than the ghosts were, so I'm not inclined to get cardinals now...
but what about the hatchets? Has anyone had RCS with hatchets? I haven't had those since I was a kid - I'm guessing they'll eat bite size RCS on leaves within a couple inches of the surface, right? Or strictly floating food? These might be what I'm looking for.
Thanks for the other recommendations, too. Would dwarf rasboras be any less aggressive than cardinal tetras? I wonder if they would wipe out 100% of the RCS babies.