some articles says that you need at least 10 gallon minimum to breed CRS, thats not true, i have 6 in a 2.5 gallon with 2 females carrying eggs ( not shown on the pic) just good water quality and variety of food will do it
But, a lot of people keep CRS in smaller tanks, it's just a 10G is much more stable especially since you have expensive shrimpies that you are dealing with.