another sugestion is put 2 of several types of rainbow fish in like boseman and turquoise. it really make a much more spectacular looking tank when they mature. just my 2 cents.
It has passed on my mind. But the problem is that I have not found any other equally beautiful species of rainbowfish (to my eyes at least )
I was thinking of adding some cherry barbs along with the harlequins but I do not know how that would look like. What do you think?