Floating chlorine tablets are not ideal: Chlorine gas is emitted, which degrades your cover, headrests, etc, and is a health hazard. Use granular di-chlor. And test daily: Before you get in the spa. Add X amount after. Next usage, test again: If your chlorine is low, double the dosage and keep adjusting over the next few days until the right amount is found. pH and alkalinity are keep in keeping your chlorine working to its maximum efficiency.
Hope this helps. Good luck moving forward.