I've seen the magic additives make a huge mess in septic pipes and systems. One place where they switched to enzyme treatment over having tanks sucked out with a vac truck ended up with systems full of a cheese like solid masses that plugged everything off. They ended up bringing in vac trucks with a pressure truck to try and clean it all out, it took days.
You're best to just to spend your money on regular cleanings and stick with one vac truck company that records the amount sucked out. I've had two houses with septic systems, the first house the previous owner was having the tank cleaned out every year by a different contractor every time. I used the same company every year to keep the same frequency as the previous owner, on the third year, the company told me they weren't getting enough out of the tank to really justify cleaning it every year, and that the tank was grossly oversized for the house and usage, and suggested that I only have it cleaned every 3 years. Kudos to them for being honest and saving me the 300.00 charge every year. They said the tank would function better on a bacterial level having some accumulation in it to keep the temperature up in it.
On my second house with a tank, the tank hadn't been cleaned in 10 years by the paperwork we were given with the house, I had it sucked out and the solids were just about over the wall in the tank. That's how septic fields get plugged, this one is still gravity draining and doesn't look like it needs a pump added yet, so I dodged a bullet there.