Help and Advice

i was reading the other day that someone with the same tank as me (interpet rr94 nano) had replaced the filter media in the back compartments with "live rock rubble" and not muh else. i currently have a nano protein skimmer waiting to go in the tank aswell as a small internal filter i am going to use with rowa phos inside. just wondering if anyone could advise me if this is easy to do or should i just stick with the media at the back?

thanks matt