I have a 30 gal aquarium with 4 goldfish, 1 black moor, a dojo louch, and a few other goldfish types. The black moor is "floating" vertically, struggling to maintain a normal position. Whenever he starts floating right, the gentle current moves him on his side or something. I don't know what disease it has or anything, so if you have any ideas, I'd be grateful.

Head down or head up?

sounds like swim bladder dissorder, is he still eating ?.... if so try and get a slighty boiled, un-salted, de skinned chopped pea into him
if he doesnt eat the pea, fast him for a day and then feed the pea but once they are that stage i recomend u try to get him to eat a small chopped pea right away,

Kev

His head is down most of the time, and he eats still. I'll go to the store and get some peas.

Head Standing or a fish swimming head down is usually due to an inflammed swim bladder which is possibly viral.If the fish does not get better after a couple days of peas it is most likely caused by a virus.In which case is may be infectious and could spread.Viral swim bladder inflammation is not curable to my knowledge.But can be slow through antibiotics.Feed him the peas after the fasting and let us know if he improves at all.