I have 3 blood shrimp in my 90g.
I had 1 in there, but he hid for the first week.. never saw him. Then I learned they like to be in a community, so I bought 2 more... sure enough, a few days later all 3 are always out, those things scurry all over the rocks like mice, always moving. Though they DO fight with one another whenever they cross paths, I have yet to see any injuries. They also leave all my fish alone from what I've seen.
The other kinda cool thing they do is, if you put some small floating food.. (i.e. flakes, krill, etc.)... they will climb up to the highest rocks, then "run" up the glass (using their 'fins' at the bottom of their tails for propulsion), then go upside down at the top of the water and 'run' across the water upside down to snag a big piece of food, then swim back down behind a rock to eat it.
Very interesting how they interact with their environment. I would've liked to have had a skunk shrimp too though.