The EPA approves only 3 chemicals for sanitation in swimming pools & hot tubs; Bromine, Chlorine, and a chemical with a much longer name but abbreviated PHMB. To be in compliance with federal regulations at least 1 of these must be used for sanitation.
We are all familiar with chlorine as it is by far the most common method used to sanitize swimming pools. It is not as good a sanitizer as bromine but the major reason we do not recommend it for hot tubs is simply water temperature. Chlorine will dissipate out of water above 97 degrees.
Bromine has been used in the hot tub industry for decades as the primary sanitizer. Both chlorine & bromine are chemically known as halogens. Halogens have a unique ability to both sanitize (kill bacteria, viruses, etc.) and oxidize. Bromine is simply a heavier atom, hence the reason it will stay in water above 97 degrees. We strongly recommend the use of Bromine (Br).
Bromine can be introduced to your hot tub with any of 3 methods: a Floater (Feeder) with Bromine (Brom) tabs, combining a Bromine Salt with an Oxidizer, or a true Salt System.
PHMB is polyhexamethylene biguanide, hence this method of sanitation is often called "Biguanide". Biguanide is an effective sanitizer. It was developed for the medical industry several decades ago. However it has a very significant downside. Biguanide is incompatible with all other chemicals you might use for your hot tub, even ozone. Hence the oxider for biguanide is hyrdrogen peroxide, not shock or ozone.
You must be very careful and attentive if you use Biguanide in your hot tub. Bigiuanide is known to cause problems with filters if you are not very careful to not introduce anything incompatible with biguanide to your spa.
This is technically a "non-chlorine based shock". Shock is an oxider used to remove (or oxidize) waste matter in your hot tub. Dead skin cells, dead bacteria and viruses, body oils, etc. are all waste that needs to be removed from your water to keep it clean and pure.
Please click here for more information on Shock.