Mirror in the fishtank

I have been having problems with a hyper-territorial green terror in my 75
gal tank, he killed a gymnogeophageous meridonalis, a jaguar guapote, two
plecostomus and a synuspillum, chewed up two severums and a red devil so
badly they had to be removed, beaten up with no tails.

Thing is, I like this green terror a lot. My girlfriend likes it even more,
mistakenly thinking it's a female, she named it Brigid for the Celtic
Goddess of war. So I want to keep it, therefore the obvious answer to trade
him in or flush him isn't an option, at least until everything else fails..
I want to exhaust every other option first.

So I've been trying various methods to curb his aggression. I put in
several silver dollars as dithers, he chased them for a while but when he
realised he couldn't catch them just gave up and now ignores them. I put in
a couple of mbuna (a cynotilapia afra and 2 demosoni) and he chases them
occasionally but still picks on the other weaker fish more (usually
targeting one at a time). I put in a pair of convicts hoping they would set
up a territory and be able to defend it from him, which could absorb alot of
aggression, but he's been able to prevent them from settling in anywhere and
persecutes the male mercilessly. I put a large Oscar in the tank hoping he
would be able to keep the peace (this has worked before), but even though it
was twice his size, the Green Terror quickly intimidated him and now the
Oscar is sulking on the bottom, refusing to eat.

Finally I tried an old trick and put a little mirror from my neighbors
cockatiel cage in the tank. This has finally seemed to work to some extent.
The Green Terror spends hours squaring off with the mirror, posturing in
front of it, wagging his tail, swiming around and a round it, and just
staring at it sullenly from behind a rock (the mbuna and the female convicts
also freak out on it). He finally saw a face he was scared of.

My question now is, will the mirror leach any metals or glue into the tank
which could hurt the fish? Can I leave it in there for a few hours a day or
not? It doesn't seem to work as well when taped to the outside of the tank
but I could do that as second tier alternative.

Any other ideas on reducing this guys aggression would be welcome too.

Jr