Im going to have to agree with Mystic on this one sorry Henward.
I to love big fishies. I personaly have never played trial and error because i think it is just cruel.
Research is the key to keeping big fish. and yes you will come across people who have managed to keep mutiple big fish togeather but most of the time the fish are not happy and die before their time.
If i was you i would be having a good look at what you allready have and see why maybe some of your fish are not eating, biting each other ect.
And dont come crying to us when it all goes to hell. I have seen it all to often and im sick of rescuing peoples fish.
Thats enough from me.