ToIm thinking possibly serpea?
Terrible choice. Extremely nippy. In my opinion, a species to avoid and one of the most common "beginner's mistakes" in the hobby. Was certainly the first fishkeeping mistake I ever made.
Hyphessobrycon eques and its relatives are schooling fish best kept on their own. On the plus side, they have a true feeding frenzy behaviour, and while that means they attack everything else in range including each other, it's quite fun to watch.
I like rummy nose aswell?
A delicate species that needs soft, acidic water to do well, or at worst, medium hard, neutral water. Waste of money if you have hard water. Looks lovely in large groups, but quite large, and not worth keeping if you're only going to get six of them! You need at least a dozen before they earn their keep.
If you have hard water, or you're a beginner, consider the x-ray tetras (
Pristella maxillaris), a species that is both hardy and able to thrive in hard, alkaline water conditions.
Unless you state your water chemistry here, recommendations for tetras are a bit meaningless, since most of them only do well in soft, acidic water conditions. Oh, and the aquarium size matters. Most tetras need at least 15 gallons, and species like rummynose tetras 30 gallons plus.
Cheers, Neale