How large do the WCMM get and do they school well?
I have a Fluval Spec V (just a notch above 5G). After looking at the tank, its clear i'd have to go with some micro rasbora for even a decent schooling fish. I don't know how CPDs do in that respect.
For now, I have pygmy cories also planned for this tank as well as cherry shrimp. We'll see how it goes!
Go get some microrasboras... WCMM will get too big, and these guys once they grow will join my school of WCMM in my 40b, as of right now they'll get eaten in there though.