PLEASE HELP IN DIRE NEED!!!

[ekir989]

I have a mixture of wild caught brazilian and another group of wild caught. They are destroying each other by night but I can not tell who is fighting who. I plan on doing some isolation tanks because these fish are important to me.
Any recommendations on how to stop the fighting? My tank is a 55 with 5 6'' discus in them which might be the immediate problem.
Is this a matter of fighting over female?
Space?
Food?
Please help any feedback would be appreciated.
Thank you

[boxters]

I had the same problem with my wilds. They were always good together, then suddenly one day they became very aggressive , and a few days later a pair laid eggs.