Medina makes a very good product called Actina. You'd have to contact them to see where it can be found here. I know that AGOrganics had some at one time but not sure about now. I can tell you just from smelling it that it has molasses in it. It helped my parents' septic system tremendously when they had a bad time with it. It has the microbes in it, and some sugar to get them going. They had killed theirs off with household products that shouldn't have been used.
I know there have been some other strings on here regarding this system, so take a look around. Mainly you keep the microbial activity high enough to keep the material digested, and the roots from growing in. the moisture is a given. I believe the product label recommends a monthly additional dose, which isn't expensive and well worth it.
Hope that helps!