I use the liquid Camco blue or green, depending on what WalMart has in stock. I use the individual bottles. One per tank and one when I empty between trips with about 2 gallons of water/Dawn/Calgon. I'm probably overdoing it, but I don't have odors and so far everything seems to flush out of the tank when I empty and flush it. That liquid is supposed to have a mild digester that hopefully will liquefy any left over solids.... at least in my mind that's how it works and it makes me feel better... LOL!