What kinds of fish will not eat CRS?

Otos are the only fish known not to eat fresh water shrimp.
For all others, if the shrimp-let will fit in their mouth, it's dinner.

People will report that they had no problems with such and such a fish, and that's fine for them. That is usually due to the shrimp colony being large enough that predation isn't noticed rather than no predation occurring. Once you get a breeding colony established there will be enough activity in the tank that most of us wouldn't care that there were no fish. If you insist on fish, lots of plants and cover will help protect the shrimp.

Yep, what he said. Also cories, they may go after babies though. If you keep fish, keep them well fed to minimize loss.

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i really haven't had any problems with small species like CPD or the two dwarf rasbora species i've kept before in my shrimp thanks.

I've got Harlequins with my RCS. I've never seen them go after even the smallest shrimp, but when the harlequins laid eggs the shrimp were all over them! I also have some emerald eye rasboras that stick really close to the surface and I doubt would ever go after RCS. These guys are small and tightly schooling and are never lower than a couple inches from the surface. I also have cardinal tetras, but I see them spooking around the lower levels of the tank and suspect they might snack on tiny shrimp. I have about 6 of each species in a 55 gal with countless RCS. If they are eating some, it isn't affecting the overall population much.
wren

At one point I had Rams, Betta, Tetra's, Kuhli loaches, platys all in with RCS and the population kept rising. I figure as long as you don't have fish that will hunt down the adult shrimp and have some cover for shrimplets its pretty hard to stock a tank to have negative impact on RCS population.

Some marbled hatchets would be good with them

otos, guppies, neons, cardinals, hatchets, flame tetra, congo tetra