I have kept them for years along side cleaner shrimp and fire shrimp without problems.
When I had a 125g reef tank my Frimandi would swim out and about in the tank. Since I got the 400 I have had several different Frimandi - including 3 at a time, and they have found territories that they staked out and kept to those areas without swimming out in the open.
At one point I was lucky enough to get a wild pair - and those 2 found a spot in the back of the tank, facing the back of the tank they called home, and I only caught a glimpse of them rarely when struggling to look for them.
When they are out and about they are stunning fish. And I think the wild ones have a little deeper coloring and more brilliant metallic blue eye lines.
Dave B