Well Put Rakie.
I agree, but I thought "large Red Devils and Goldfish" meant adult fish and that might be a bad idea IMO since they can be 10-12" fish or bigger I suppose. I've always thought (and read) 90-100 would be the minimum tank for one of these fish for life. I have never kept them
In a 55 that is 12" wide with decor, a single specimen could have trouble maneuvering not to mention a pair. And water changes would have to be done quite often. Thats how I was looking at it
PS your avatar kills me