Water changes in quarantine tank?

Hey all!

Yesterday, I noticed that my betta Buzz was floating a lot and swimming sideways and so I did some research and it turned out he had swim bladder. I set up a Home Depot 5 gal bucket with roughly 3-4 inches of water (maybe 2 gallons id say) and added a heater and some floating plants. I will be fasting him for around 2-3 days and this is my first time doing it. Does anyone have any tips on how often I’d need to do a water change to keep the parameters safe? Tysm!