Good suggestion.
I will have to see the rainbows and the columbians in person to gauge.
My initial thought is that the columbians are too dense at adulthood for my tank.
I still want the Sev to pop in size and color -- but I do like the columbian colors as they will accent his orange/red.
The Panax...looked at a pic or two, they look like big killifish. Are they fast enough to get away?