Catch 22. When they run out of a food supply, they WILL eat plants, fry, shrimp, mystery snails, and each other.
They are opportunists.
Keep them fed, they reproduce at an alarming rate, and foul your tank.
Starve them; you starve your shrimp.
A community fish tank will keep them in check or even eradicate them.
Shrimp/snail only tank-outlook not so good.
If you put fish to get rid of them, that compromises the shrimp.
My experiences with them, anyhoo.
(Not with shrimp, but snails and plants. Had to nuke the tank.)
-Stef*