Brian,

First, let me say that the chlorine products are all far better than nothing. However, virtually all the chlorine products have the same drawbacks. 1. They are very dependent upon both water temperature and organic content. Lower water temp and higher organic content both can seriously impact the ability of the chlorine to kill the bad bugs. You can, to a degree, overcome lower water temps by longer treatment or higher concentrations of chlorine. Chlor-Flock attempts to overcome the issue of organic content, and works to a degree. 2. They will not reliably kill Crypto and some other similar hard cysts.

The Puritab and Aqua Tab tablets are very small.

Due to quirks in U.S. law, such treatments are considered pesticides. U.S. approval requires expensive and very demanding testing to prove efficacy. To date they have not successfully completed the testing. Lots of promises over the years, talked to all the manufacturers, but no success to date, to best of my knowledge.