Check out springer's damsel (aka sapphire damsel).
I have one in my 30g with my 2 clowns, a ywg, and a purple firefish, and he is the star of the show, and not aggressive at all. From my research, springer's damsels are one of the least aggressive of the damsels. They are super bright and beautiful too.
This is Stu, my springer's.
