Chlorine doesn't last as long at the elevated temps (or so I remember reading somewhere). Bromine is better. I bought a jug of bromine tabs ($15) and they lasted me nine months, so not a big expense there. I have a floater and put one or two new tabs in once a week. I tried using muriatic acid, but would always overshoot my target ph, so now I use dry acid (also very cheap). When needed, I do use borax as ph up. I also shock once a week with a non-chlorine shock (also very cheap - I think like $3 a bottle that lasted seven months). I've found the hot tub maintenance to be very cheap and easy. Your milage may vary due to frequency of use and any "beverage" spillage or addition of other organic compounds :-)