ac/moisture for a sm fish room, ideas?

[Elliott]

I have a small fish room off my garage with no windows. It's currently conditioned off the main house ac/heat ventilation system with one duct, however it quickly gets too hot in the summer and needs it's own unit. There is a bathroom style exhaust fan in the ceiling but when left on the temp rises due to conditioned cool air being removed. When off the humidity feels like, well the tropics!

Anyone have a recommendation of a small efficient unit for this application? I'd like it installed on the roof out of view.

many thanks

here is a shot of the room

[IMG][/IMG]