I have two flame angels that seem to get along wonderfully, of course time will tell if they are actually a pair.
I bought two small flames, and was bigger than the other, and placed them in my sump together for observation. My sump is a 150 gallon rubbermaid stock tank with live rock and a DSB, so they had a nice habitat to bond in. For about five minutes there was a little twirling about and displaying, and then it was as if they said, "OK, Your cool." They are best buds now. It is too precious to see them swimming together. I observed them in the sump for a while, each time I expected to see a mangled flame angel corpse floating, but they were still together so I added them to my reef.
Of course the same day I put them in my 155g reef one began to eat my sps corals. :roll: So I had to catch them both and they are now in my fish/softie tank, and they are still friends.
I really hope they spawn for me, they both have the same hidey spot in the live rock, so I am thinking that is a good sign.
If you were to try and pair your C argi, I would remove him, add two small ones, and then add the original one. I think that removing the original one first (for just a few hours or so)would allow the new ones a chance to get their bearings before they have to interact with the original one. Or if you don't want to go to the trouble of catching him, I would at least add the new ones after the tank has gone to sleep for the night.
I have a great book at home that goes into detail the spawning and haremic activity of C argi. It's called "Reef Fish Behaviour of the Caribbean" or something like that. I am at work now so I can't see who the author is, but I'll post it later if you are interested when I get home.