The movement nationwide is for on-site retention of all waters. This solves a variety of problems associated with increased water volumes into the creek, flooding, erosion, scouring and destabilization of creek banks, etc. So we are faced with using the best available technology to keep our septic systems functioning properly. Using lack of percolation to limit growth may need to be rethought. Added enzymes are somewhat controversial.
Some products are good, lots are full of sawdust filler.
One of the few that has been tested is Septic Flow Plus, which is both EPA and FDA approved. Paul, Dick and Andrew Rasmussen of BioSolutions suggest that these approvals be used as a guide for selecting a product. The super strains of bacteria and enzymes in these products can unclog a system and help reestablish the decomposers after a tank has been pumped. If you are worried about the quality of water from your tank, there are many local labs that will test for BOD and total dissolved solids. There is a strong movement to develop a way to monitor and maintain septic systems by certification.