i had cherry shrimp in a vase with some java moss and no sub straight, the bred like crazy at my moms house despite not a single water change I'm 4 months. i think it was about 2 gallons.
Yeah they breed pretty easy, they breed enough to keep their numbers on the rise in my 29g with 2 bolivian rams and a couple loaches, along with platies and guppies. They're like guppies or platies if you have a male and female you will have babies.
I have red cherry shrimp, only females so that they wouldn't reproduce and they are the brighter ones, so it's nice as a mini display tank. 4 in the 1/2g, and it's the stupid plastic "betta" bowl