Maybe a GloFish rainbow shark? lol, just joking
My original idea was Australian Rainbows. The Boesmani were the ones I was leaning towards to get the blue and yellow colors in the tank. But Ive seen a couple other fish I like that would be less expensive. I was also considering Roseline sharks or maybe even a school of Rosey barbs or Congo Tetras. The original plans were to try a SA theme but I cant find a tetra from that catch location to fit the right size and color idea.
There aren't many SA tetras that combine size with color; Bleeding Heart Tetras (
Hyphessobrycon erythrostigma) come to mind, but finding really nice ones these days is almost impossible, and in any event, I doubt that they have the size you require.
Like
@lloyd378, I'm not a fan of the Australian Rainbows in this context, they're just a bit too hyperkinetic.
Congo Tetras (
Phenacogrammus interruptus) would be a great choice if you had a school of 12+ fishes, but the downside here is that they take a long time to reach their full size, and commercially available specimens tend to be pretty small. They also do best in heavily planted tanks.
Roseline Sharks
(Sahyadria denisonii, a.k.a. Denison Barbs, Red-line Barbs
, etc.) are nice, but if you can find them, there are a couple of closely related Cyprinids from southern India that are somewhat larger and decidedly more unusual. They are also pretty mellow. One is
Dawkinsia filamentosa, the filament barb, shown here-
A closely related fish from the same region is
Dawkinsia assimilis, the Mascara Barb, shown here-
If you were lucky enough to find both, they can be kept together.