Two major points:
1. Aquamira tabs aren't meant to be used separately of Aquamira filters and, as far as I am aware, are utterly ineffective against both Giardia and Cryptosporidium. Water treatment is, therefore, null.
I believe you are thinking of a different product, perhaps their other tablets for improving the taste of stored water. These are, indeed, purifiers and effective against G. and C.
http://www.aquamira.com/consumer/aquamira-water-purifier-tablets-12-packEdited: Welcome to ETS.