Actually, what Calgon is good for (and for those of you who don't know - this is NOT the calgon you use in your bath - this is Calgon that is harder to find - the old fashioned Calgon for laundry) - but it is supposed to help keep the sides of the tank slippery - and that also keeps the rods easier to open and close. Now, actually ANY soap will do that - but you don't usually put soap down the toilet - so the GEO method added calgon to it to keep things slippery. Me, I just take some of my dishwater and put it down the toilet occasionally. Or I use the water from doing my handwashables.
You have to be careful - if you use chemicals - don't use the calgon method and vice versa. And the chemicals are supposed to keep things smelling fresh and oil the rods, etc, too.
But no matter which method you choose - the most important thing - USE ENOUGH WATER. And use a tp that will break apart in water - and if you go back to my post on that elsewhere in this section - you'll discover the best are Scott and others like it - better than the ones made specifically for rv's. That's true for many products made specifically for rv's. Unfortunately.