Without knowing your frequency of water changes and how you maintain the FX6s, it is hard to say. As reference I used to run a 75g with 8 adult silver dollars and a few cories, and filtration was a FX6 and an Aquaclear 110, with prefilters and weekly water changes. Your tank is several times larger, and the rays substantially messier.
Because of the foods the rays eat, an aggressive water changing and filter cleaning routine is needed, and I would not run any filters without prefilters that are cleaned weekly or more often. Just my opinion, others including you might disagree. Good luck!