Many failures in using halogens are due to improper use. Check expiration dates. Liquids are corrosive and stain. Theoretically, iodine-treated water may be a problem for individuals with thyroid diseases and also during pregnancy, causing goiters in newborns. Likely, drinking such water for a week or two causes no problems.
Halogens have an unpleasant taste, especially at higher concentrations.
These substances should be added after the necessary contact time. Sodium thiosulfate reduces iodine or chlorine to iodide or chloride which have no taste or flavor. Sodium thiosulfate is non-toxic and available in chemical supply stores. Filtration imparts no taste and requires no contact time. Filters also remove sand, clay, and other matter, improving water taste and appearance.