Here's a tip I read on another forum a while back. Aquillas can be fought in the colloseum so if you bring somebody like gogo with steal, steal, steal, thief knight, sneak ring and running shoes it should be quite easy. I forgot which items to bet to fight one though so you'll have to do a small bit of research. Remember though, only one in every eight Aquillas will actually have an Economizer and the rest will have phoenix downs. Does that help any?