Many hobbyist just entering the hobby will have “sticker shock” when they see the prices for good quality live rock.  Sometimes this will result in some people t trying to find the cheapest approach to filtration.  This is the wrong approach to take.  Cutting corners on your filtration will always result in long term difficulties.  The below links can better explain what I mean

 https://www.reefaquarium.com/2013/common-approaches-to-filtration-in-marine-aquariums/

 https://www.reefaquarium.com/2013/some-algae-scrubber-basics/

http://www.advancedaquarist.com/2003/2/beginner

http://www.reefaquariuminfo.com/the_filters.html