external skimmer-I am building a new sump using a 40 gal, so i am looseing about 10 inch from the 55 gal I have now. If I mke the skimmer section 12 to 14 then my fuge protion will only be about 8 inch. Thats why i am thinking external. otherwise, I will have to find a skimmer with a small footprint including pump.