FW Filtration Help

[butters88]

Hi guys
I've been having problems w/ clean water in my dad's tank. It's a 90G stocked w/ a 18" silver aro, 2 5" blood parrots, 2 3" pink convict cichlids & 3 3" common plecos. Its filtered by an aquaclear 300, fluval 2+ submersible, and 404 cannister. Problem is the water never really seems clean and clear, even after I clean the filters. Seems like the water is full of small particles all the time Should I add more filtration? Any suggestions would be appreciated!