I just put a FX5 on my 125 and want to know what the best setup for it was. Right now I have some pre filter and biomax in it. And I also wanted to know that since I have a AC110 and Emperor 400 on it. Is this overkill.
Overkill is reletive to your stocking/tank size. For a 125 gallon with "normal stocking levels" I would say your well filtered. In my FX5's, I use all three trays for biomedia and only use the stock sponges for mechanical. I do not use/need chemical filtration.