I have a 75 gal now with 20 cichlids in it. Coworker is getting rid of a 90 gal tank (only $100) and want to upgrade. I need some suggestions on best way to go about this. Current filtration is 2-AC110 and XP4. Should i get any other type of filtration/water movement?? Holey rock for decoration sitting on egg crate, crushed coral for substrate. Any help would be appreciated.