A ph of 8.2 will not harm your betta provided the other values are in order. Many bettas are kept at that ph and higher to no ill effect. But something in your tank is elevating the ph from 7.4. Normally, ph drops over time due to waste matter, decomposing vegetation etc. The usual culprit for a rising ph is the substrate. What are you using? Is your tank fully cycled?However, I’m worried about the PH in the tank. My API test kit reads a whopping 8.2…
I agree that you should not use chemical means to lower it. Just be mindful of you ammonia readings since ammonia is far more toxic at a ph north of 7.