would a community tank of 55 gallons with 1 BROWN ghost knife, 1 rope fish, 2 candy stripe plecos, 1 goldfish, 1 opaline gourami, 1 three-spot gourami, and 1 gold gourami get along good together?
you cant have a gold fish in a tropical tank, and unless the gourami where all females they will rip each other apart. I cant comment on the knife and I dont know much on plecs
Substituting fish with more gouramies is a VERY bad idea - as already mentioned, those gouramies (which are all the same species BTW) would be very aggressive towards one another and adding another isn't going to help. I suggest you do some internet searches on the fish you are interested in and research them in books and the like. google.com is always a good place to start.