actually, every fish would like to have their tank planted. besides, it feels much better for us to watch...i kept a dozen of male guppies and one by one past out in a week because i didnt plant my tank...
if you want colour, then cardinals are the best ones, but if u want colour and activity, i'd suggest glowlight rasboras, and if u only want activity, then danios would be perfect. ..
some note anyways, cardinals are harder to keep, since they're easily stressed, wether it's the water parameters[esp temperatures and pH] or their food...
i'd really suggest u to pick the rasboras, very2 cute, and they swim in the mid surface strata, unlike most tetras[mid bottom swimmers] and guppies+danios[surface dwellers]. .. i dont actually like danios anyhow. ..quite boring colours. ..