What sort of goldfish are the moor's companions? Is he the only fancy one of the lot? Moors have long flowing fins and are not very good at swimming (same can be said for many of the long finned, fat bodied goldfish). Depending on what other type it has been crossed with it may also have those stupid (my bias is showing here :lol: ) googly eyes so will have trouble finding food as well.
If it is smallest, and the others are faster swimming comets or a faster swimming type, it will be intimidated. The others will also be beating it to the food so it is possible it will starve to death.
I don't have trouble with long finned goldfish being in aquariums, assuming the are large enough, but I do believe short finned varieties should only be kept in ponds.