al_novak

You can use https://poolchemicalcalculator.com/Pool-pH-Calculator.html to help you factor what you need to balance your pH. You'll also want to balance your alkalinity, there is a tool for that there as well.

Chem geek is correct. I like to use https://poolchemicalcalculator.com/Pool-pH-Calculator.html to figure out how much to add to my pool.

If trying to use a chlorine generator with Magnesium will more than likely cause the salt system to read incorrect salt levels and have errors. Mineral salts will also cause issues with chlorine generators and their ability to measure salinity. Plain sodium chloride is what most systems are calibrated for. I use https://poolchemicalcalculator.com/Pool-Salt-PPM-Calculator.html to balance salt ppm.

Salt is a dissolved solid so the only way to reduce ppm is to dilute. If you're not losing water, it's possible the test you are using is not accurate. Some digital meters need to be calibrated and test strips can get old. I use this salt calculator to factor how much salt to add to the pool.

I've had experience with ozone systems on multiple pools and the large bubbles are always a problem. My hypothesis is the size of the bubbles depends on the plumbing along with the flow rate and head of the system. Air/ozone gets trapped in air pockets in the plumbing and as it builds it eventually bubbles out in big bubbles. The size of those bubbles coming out of the air pockets very based on the flow rate and head of the system. Most ozone systems use a venturi to create suction and they increase head while reducing flow and that favors larger bubbles. Not much you can do unless you add a degassing chamber. You could also try increasing flow rate.