I happen to like chromis, lol. I will admit that I started with 15 and now have 11. One died the first day and I have no idea where or what happened to the others. This is over a period of about a year.
Check out some sandsifting gobies, if you arent planning on corals on the sandbed that is. lol
I also like the gramma idea and I think no tank is complete without a lawnmower blenny. Youve got a nice sized tank and can have several small-ish fish which is super cool.
Do you have a lid over the tank? Then you might think about a firefish too.