I just use the cheapest mouthwash that Walmart has; about half a cup to each 5 gallons of water and everything comes out minty fresh. About $5 for two bottles and lasts all summer.
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Unless you are knowingly diving in polluted water I see no reason to disinfect conventional open circuit scuba.
In fact, I would avoid doing so unless I knew that the product I was using was safe on the rubber and plastic components (the classic example of incompatibility is silicone spray and silicon second stage diaphragms).
A good soak in fresh water (making sure no water enters first and second stages of your regulator) followed by a further rinse and hanging up to dry should suffice.
If you're concerned about bacteria then a few drops of ordinary dish soap in a bucket of water, slosh everything about in it then soak in fresh and rinse then dry. Don't go overboard with the soap and rinse thoroughly - lemony fresh scent is fine in the kitchen but not so pleasant underwater. Soap is great stuff, kills ebola and pretty much everything else .