Sounds like one of the rare times a Pet store employee that is well informed. They do indeed need a mature tank, since they eat microbes that are free floating in the water column.
I would be cautious with the loaches, not the best tank mates for any shrimp. Make sure that there are places for the shrimp to get away, particularly when they have to molt.
BTW, from your excellent pictures, it looks like you've got a pare of males.