Basically, I'm looking for another shoaling species that will hold their own in the tank. My Serpaes are nippy, my loaches like to "explore" the other inhabitants of the tank (aka, feeling them with their barbels), and overall the tank is semi-aggressive. Danios are too small, as I need something that won't be eaten by my African Butterfly Fish.
Congo tetras are too large unfortunately. Due to space constrictions in the tank, the tank isn't really large enough for them, and I wouldn't have room for a decent-sized shoal.
I'm basically looking for something similar in temperament to a Serpae Tetra, that is around the same size, and that is a different colour.