First off, I am very new to photography (other than point and shoot) so I am pretty clueless about most things in this hobby. The main reason I purchased my new camera (Canon XS) was for aquarium photography. The best pictures I have seen use a flash on top of the aquarium and a flash on the camera. My question is, what do I need to purchase to be able to use two flashes? The flash built on the camera would probably be fine for the on camera flash but I can buy another one if necessary. I also have a Canon 430EX II flash being delivered today. I would prefer to not spend any more money than necessary.