Neo Multis and friends..
My son has a 20 long with a small group of Neo Multis that have been pretty consistently for a year now.. geez has it been that long?
Anyway- the adult Multis seem to be pretty capable of holding their own and did so for a couple days in a mixed tank until they were moved to their own species tank.
I agree with Longstocking.. Julies should be fine. Only thing I have found that Julies tend to weed themselves out and ignore the rest of the tank. As long as they have their own rock work.
Another thought if you like shellies is the Hecqui. I bought 6 from another member and have them in their own tank. Unfortunatey 6 became 5 quickly, then 4. I later moved one out and have 3 together and the 4th is doing great in a community 20 long with a couple smaller Z-rocks, some petricola, and a couple small yellow labs. The Hecqui get bigger then Multis and I would not be afraid to put them in with a variety of larger fish. I probably wouldn't put it in with large Haps, but I am sure you get my point..
Cool fish either way! Good luck..
-Marc