We recently purchased a redwood hot tub with snorkel stove that seats 6 or so people, I think it is 8 feet in diameter. We bought it "pre-owned". The person we bought it from didn't use chemicals, he would just change the water after a few days. I have been trying to find information on the internet about keeping the water clean without using chlorine or stinky chemicals. We'd like to find a natural way to keep it clean without having to empty it after a few days. I don't know if there is a way to do that or not. We are having a bunch of friends over this Saturday, do we need to be concerned about bacteria developing right away? Any advice would be appreciated.

24hr corona discharge ozone with circulation pump and venturi injector - definetely the best way to go - minimal chlorine requirements and balancing - does not affect ph, allergy friendly, odourless (except ozone fresh smell)
unfortunately from experience i do not endorse any system claiming chlorine free - a small amount is always necessary for trouble free proper sanitation, but ozone means you need very little - a few teaspoons a week at most. must have clean filter, be clean - shower first - then its perfect