Mixed tetras?

[shrimpchips]

The serpaes should be fine with cardinals/neons. The bloodfin will, as you have found, rip the shat out of the little ones.

I've found that most of the deep bodied tetras are relentless fin nippers/fish killers. I once had a single large Rio tetra that killed everything else in a 20g.

[Leah]

Maybe that is how it got the name blood fin.