Pea Puff Attack!

I have a 20 gal long moderatley planted, but with fair amount of line of sight breaks to prevent aggression. In the tank I added 3 pea puffers (all the store had at the time) but today more got out of quarentine so i bought 3 more. I was hopeing to diffuse some aggression in the tank by adding some more and 12 ember tetras. When I added them one of the new one bit another puff boy! I have hime separated right now but do you guys think I should return him or give him another chance?