[travelin texans]

Just a thought, these miracle tank chemicals with active bacteria what happens to that bacteria when you clean the toilet with a bleach based cleaner or some other strong cleaning agent & if your bath sink might be plumbed to the black tank & regularly use anti bacterial soaps.
As for septic tanks they are a total different system than rv holding tanks, nothing you put in rv tanks will be in long enough to break down matter & as mentioned if it will break it down in a matter of hours I would be very wary of using it in my tanks.
If you're happy with whatever you use, keep using it, just keep in mind it's probably not any better than the fabric softener/soap method at breaking up paper/solids, just cost more.