Your impression is a correct one! Nature2 by itself is not enough. Ozone, by itself, is not enough. Combine the two and it's almost enough.
A little residual chlorine never hurt!
When you add di-chlor after each use you are indeed "shocking" the tub. Your weekly "shock" may not be needed but it sound like it's working for you. Try dropping the extra "shock" and see how it goes. If you have problems you can always add it back to your routine.
Good Luck
Okay we are going to border on where I get outside my leauge. ...
A shock breaks a certain level of chlorine in the tub. and oxidizes the contaminets that chlorine has killed and frees up the chlorine so it can continue to kill bacteria.
So, if I have enough free chlorine in my tub, I don't need to shock.
You can use a product thas has MPS to shock, or I have also heard you can add a "super dose" of chlorine and achieve the same results. (Oxidation and freeing up of the chlorine).
What I don't get is, folks who are using no chlorine, Ion and ozone to kill bacteria, since no chorine is being used, the shock is doing what? Burning up the contaminets that that ions and the 03 killed?
But not freeing up any chlorine, because they are not using any ?