Well, I added a single Firemouth of the same size to the 40 gallon with the Blue Acara as mentioned above, (but I thought I would add a newer, more detailed post of what I have done), and that didnt work out good. I was surprised the Firemouth was constantly chasing the Blue Acara around, and the Blue Acara did not stand his ground. So I removed the Firemouth, and put him in my only other tank (55 gallon) so my Blue Acara would not be harassed. Yes I put the Firemouth in with a larger female Green Terror. The Green Terror did not do too much, other than every time the Firemouth would come near her driftwood home, she would just chase him away, but not very aggressively. So I am thinking, maybe the Blue Acara would do better with the Green Terror as they are similar and swapped them out so I could keep my all SA tank. It seems to be working better than with the Firemouth, so I will keep a close eye on them and make sure the Green Terror doesnt do any damage. She isnt as fast as the smaller Blue Acara or Firemouth for that matter, so we will wait and see.
If push comes to shove, I will just have to sell the Blue Acara or Firemouth and start over with a plan.
I hope this works, as I would now keep the Firemouth in the 40 breeder, and make it into a CA tank.
Art
P.S. Keeping my fingers crossed with this experiment.