All pros no cons in my book . They actually don't remove anything .the growing algae uses no3
to grow . They then are removed when you do your screen cleaning every 5-7 days. I have a 40b where the scrubber is the only filtration and it holds a 0 no3
and .04 p04 with monthly water changes. My 180 gallon uses both an algae scrubber and a skimmer. I have even experimented by turning off my skimmer for a month on that tank and nothing changed . I couldn't imagine trying the opposite . I even go as far as drying out the removed algae into sheets and feeding it to my fish and they absolutely love it.