I thought I'd just relate a recent experience with regard to Copper Tetras or Silvertips.
The fish profiles generally written about them state that they are "peaceful community fish ideally kept in schools of 10 or more".
I bought ten of these fish at the end of September to school along with my Harlequins and Rummies - they caused absolute havoc.
My Glowlights and Rummies hid in the undergrowth all the time, the Harlequins grouped together at one end of the tank and my previously serene aquarium turned into a battleground. The only fish they didn't seem to bother were the Cory's, Oto's and shrimp.
I decided they were too much trouble and, armed with my home-made bottle trap and a breeding tank borrowed from a friend, caught eight of them to return to my supplier.
She inspected them and said it was too high a range of males to females so the two left behind that I didn't catch should be OK - and they are.
She gave me 8 Blue Rasbora as a replacement....even though I told her I had spotted an error on my till receipt and hadn't actually paid for them.....a sign of a good LFS.
My tank is now restored to it's harmonious previous life and a joy to sit and watch again.
Please think twice before adding any number of these gorgeous little fish other than what appears to be a very comfortable pair - male and female.