Really digging this tank so far, the rasboras look epic in there!!!
Since you wanna hold off on rcs for a rack, how about adding 2-3 amanos? I adore mine in my communal tank. I haven't had any algae issues at all. Well until now XD I went out of town for a few days, with no timers, so left the lights on the whole time. It's only a touch dusted on my driftwood, so hoping the amanos clean it up for me soon.
I am unsure if you have reached the stocking limits yet. I'd want to say yes, with 19 ish raboras, but depending on filtration and such & how well you upkeep the tank you could prolly get away with adding a centerpiece fish.