Thanks hypnotic, I appreciate your insight.
I figure I would do pvc- like for CPOs- for hiding spots. I think I'll do it in a honey comb pattern on the back wall, as I have a 20 tall, and it will add more surface area for bio and hiding. I thought about cholla, but I decided against it since the RCM have long arms.
I'm really looking forward to them since they are supposed to have larger personalities than dwarf shrimp.