I ended up getting a Royal Gramma and a Firefish. They add quite a bit of color and activity to the tank. They seem healthy and have been eating. They get along well and the Six Line seems more confident now that it's not the only fish.
Here is a pic:
I also learned a lesson in fragging: Don't use your thumb that has putty on it to push the frag down onto the plug
Now there are dead white spots where I pushed with my thumb on the Monti frags.
The Slimer seems to to be doing ok and so does the Hammer.