Personally I use grade A leaves but from what I've seen grade B leaves are just "not perfect" leaves (broken leaves, pieces of leaves). I use a veggie clip and clip a few to the side of my tank since I have such a heavily planted tank and it takes a few weeks for them to breakdown. The thing is they break down but don't fall apart plus my BN Pleco, Oto's, and Whiptail cats often eat/rasp on them and the snails also enjoy them. Once they are getting rather skeltonized I just unclip them, remove all snails, and add new ones to the tank. They are too large to use in a filter. They say use 1 per 10 gallons BUT they can really release tannins when they are newly added so my suggestion is to add one, wait about 3-4 days and see how much color is in your water. If you want more add another leaf. I add up to about 10 leaves to my 220g if I want alot of tannins in the water. If not I only add 3 or 4.