A Question About Silver-Tip Tetra's?

Are they aggressive fish? I have 3 silver-tip tetra's, 3 glow-light tetras, and recently just bought 5 harlequins. The silver-tips however seem to chase the other species, and each other, in what appears to be an aggressive way. Could someone tell me if this harmless fish behaviour or if they indeed are being aggressive. The other fish don't seem to be stressed though.