I will be honest here, The RCS in the tank are food, I put them there so my Betta has something to hunt, At last count there were 70 shrimp in my tank, So if the Betta and Loaches are hunting the shrimp they are not doing a great job, most likely because they are too fat and lazy from being over fed.
About a week ago I scooped up a bunch of RCS and put them in a 6 foot tank, Gives my Firemouth Riddick something other than live bearer fry to hunt.
Any that are hunted down and eaten are replaced by the shrimp living in the bottom of my canister filter, I have no idea how they get in, every time I clean my filter I find about 10.
Feeder shrimp are cheap.