want another fish

I currently have a Green Mandarin, two clowns, and 2 cleaner shrimp. I would like to get another fish. I have a 40 gallon long show tank with a 10 gallon sump. Any ideas on a reef safe fish that isn't a bully? I have heard that a bangia cardinal fish would be good from the LFS but i think i am looking for something more. i know i don't have much room to work with my 40 gallon long tank but any ideas would help, thanks!