I tend to agree with imatrout there. I've got one of Greg's invetion and it does good job but I think I should have went to ADA to begin with. I am getting a surface film about every five or seven days. However, I do have one on its way. For 20 gallon which is what I've got, you can probably just use the existin filtration and hook up a Surface extractor at relative cheap price $9.00 plus shipping. Regards, JC.