My experience with an orbic batfish
kept in a 200g that was 7ft x 2ft x 2ft
prefered subdued lighting infact i only ran actinics normal flourecent he did not like the white light on at all
ate very well and was as tall as he was long (bigger than a 10 inch dinner plate ) and very thick and still growing when i lost him due to contaminated water during a water change and also lost the 3ft bamboo shark both died within a couple hours of the water change, the water was contaminated from motor oil but i did not know it until a few days after the deaths..long story short my wet vack got loaned out by my wife and the end of the vac hose got contaminated (unknown to me at the time) and i contaminated my sump with it during tank maint
mine did not like fast moving fish such as tangs and large angels, the tangs also nipped at his fins prety good, the only thing that i had luck with keeping with my batfish was the shark, and smaller fish dont work either becuase they will just be food for him as they will eat any meaty item that will fit in thier mouth
personaly i would recomend a 8ft x 3ft x 3ftor BIGGER(preferably bigger) i knowmy 7 x 2 x 2 would have been to small in the long run..