I'd be curious about the recipe as well, but not going to hold my breath for a 2012 original post.'
I just use a couple heaping tablespoons of the regular powdered Rid-X - the stuff that's intended for home septic tanks - after each time I empty the tank.
I figure it has the same microbes in it as the RV version, just that the liquid form is probably easier to use in an RV (and much more expensive).
Anyway it seems to work well as far as just the draining of the tank, but I still flush it out with one of those squirter wands that you attach to a hose and put down the twalet.
Occasionally the depth sensors are still fouled up, probably from some toilet paper, but I eventually get them cleared.
I'm using one of those macerator gizmos btw, because in my fixed location I have to run it 150ft through a dedicated garden hose.
2007 Jay Flight 31BHDS travel trailer