RidX is bad for a septic tank. I don't know why they are still in business. Every time poop is flushed into the tank, bacteria from your gut goes with it and keeps digesting it. At most, one simply needs to add a pound of baker's yeast to the tank about every 6 months for periodic "jump starts".
Yes, RidX will reduce the amount of solids in your tank. BUT........RidX adds bacteria types DIFFERENT from normal gut bacteria to the tank This different type of bacteria break solids down further than normal gut bugs do, causing the solids that normally settle to the bottom of the tank to be transformed into a liquid state that becomes part of the liquid in the first compartment water, which then transfers over into the second compartment of the tank and then on out into the drain field, where it will form a black goo that plugs your drain field lines and contaminates your drain field.
Worst case scenario??? Eventually, you get to dig up your entire drain field to replace the lines AND the gravel/soil of the drain field area AND you get to pay for the disposal of the contaminated soil.
It's not just septic tank pumpers who say RidX is bad. Septic inspectors and installers dislike it as well. Leads to long term problems. We always told our renters SPECIFICALLY NOT to add RidX to the tanks.