Discus are south american cichlids so ive moved this to the right area.
As a rule discus are best kept alone or with small placid tankmates like corys and tetras but i'm sure someone will come along and say theyve kept them together with no problems
as long as the bichir is smaller than the discus like the BGK will be then it will be fine,, but what ever you do dont keep ploecos/algea eaters with your discus as the will eat the slime excreted buy the discus and as the attach to the discus they will leave blisters and as discus are really sensitive then they have a higer risk of dieing from them. good luck on you quest