I ran it on a 20g. reef with three fish a flame angel, damsel, green mandrin and it pulled out a good amount of gunk.. I think it is great for tanks up to 55g. I just recently upgraded to a 46g. bow that is gonna be a sps reef and my only filtration a skimmer,refugium, and liverock so I am getting an aquac ev 120 because I need a skimmer that could handle a bigger pump. I highly recomend for your 20g.