I haven't kept tetras since college (so long ago we used wood stoves to heat the tanks).

Anyway, when I set up my office tank 2 years ago, I put in 3 bala sharks on sale from petsmart so I could tell if the tank was done cycling. 2 years , they are doing well and are in with the mixed bag of cichlids (peacocks, labs, compressiceps, pseudotropheus) and are doing great. They don't bother anyone, and no one bothers them. Exceptions to every rule.
By the way. The psychotic tank mixture will be changed in the near future. At present, everyone is still happy. I have found a little baby yellow lab, and a little peacock that made it by hiding in the holey rock.