I stopped treating my hot tub with with Halogens (bromine, chlorie and the like) and went to Hyrdogen Peroxide. It is so awesome that I had to share... If you have a tub and hate the chemicals, then check out Google, or let me know and I can give a crash course. Well worth the time and one of the better things that I did lately.
When I get my hot tub, I will run ozone and shock with calcium hydrochloride once per week and potassium monopersulfate after each use. That way, when I am soaking in the hot tub! I am not soaking in any chemicals. The calcium hydrochloride burns off completely in about 8 hours.
Calcium Hypochlorite will leave chlorine ions behind and even cause calcium deposits in your tub if you don't change the water very often and use it a lot. It is a hard-core chlorinator. It can rapidly dissipate in sunlight in short time, like in pools, but unless you use your Hot Tub in the daytime a lot, it will for-sure stick around. Did you perhaps mean another chemical that you add that is all gone in 8 hours?
The H2O2 is similar to the MPS except you leave water behind instead of sulfate and potassium ions.
What is this once-every-three-months natural stuff? I am interested.