Yea I am using it on my 40 Gallon tank , only because I already had the sump laying around. IF the sump had and option for a filter sock it would improve things greatly because with out a filter sock the sump gets dirty pretty fast. I also don't feel the refugium is big enough to add any benefit to the system. The sump also bows when full of water ( during water changes ) due to there not being a brace around the perimeter of the sump. All and all , I'd give it a 6 out of 10 stars.