Just a quick note about Aquasoil. There are 2 versions, Amazonia and Amazonia II. Recent reviews by forum members indicate Amazonia (original) is the one to purchase. I used 4 bags of the 9L to cover my 75 gal (4' X 18"). I would buy an extra bag over what you think you need. You can always get rid of the extras in the SNS, but you'll kick yourself in the rear if you come up short and have to wait another week (and pay shipping again).