Red-whatever (minor, serpae, phantom...doesn't much matter which of the 2-3 species) and pretty well any deep bodied (phantom/serpae profile type) tetra owner should be wary of the potential for nipping. Nipping is generally reduced (or at least confined to school-mates) if these are kept in groups of at least 6.
Personally, I've gotten away w/ having a few Otos & Cardinals in w/ my (large enough to be laying) angel - so far, so good, but I won't be surprised if, someday, I have an issue as Otos & CTs will both, eventually, be small enough to be added to the menu. Having a pretty heavily planted tank w/ driftwood etc. helps.
Personally, I've gotten away w/ having a few Otos & Cardinals in w/ my (large enough to be laying) angel - so far, so good, but I won't be surprised if, someday, I have an issue as Otos & CTs will both, eventually, be small enough to be added to the menu. Having a pretty heavily planted tank w/ driftwood etc. helps.