Fluval FX5 using as carbon filter
 

New to reef keeping and was wondering if I could use a fx5 filter with carbon and GFO and phosphate remover in it for my tank.
I ask as the filter has three levels and I could bag everything and put it on different levels.

Probably to much flow

You could fill it with rubble or hydroton though

It would be fine to run carbon and rubble in it, however you should just sell it and buy 2 phosban reactors. The fx5 is way too much flow for gfo, you want the water to flow through the reactor slow so it can react properly with the gfo to remove phosphates.

+1. I think it's way too big. And the maintenance on those filters sucks.

I would do as others suggest and sell it to buy a dual chamber reactor to run carbon and GFO. GFO needs a certain dwell time for it to be effective. Unless you're running a monster tank that would be a lot of carbon for your system too. The trays would hold five times as much as I would use for my 90g system.

GFO is a phosphate remover. No need to use additional phosphate removers with GFO :-)