Size Appeal: Since most Americans start their fish keeping careers with a 10-gallon tank, small fish work best for them. Not the cheapest fish in the barrel (like neons, moons, or danios), they're a definite step up at a still reasonable price. Dwarf neon rainbowfish also start developing their color potential at a much smaller size than most rainbowfish. They're still somewhat harder to find than the usual run of the mill community fish.