Do water purification tablets kill Cryptosporidium?

Mostly no. Across the reviewers we read, the consensus is that chlorine-based Aquatabs (NaDCC) and iodine-based Potable Aqua tablets reliably kill bacteria, viruses, and Giardia, but they do NOT reliably inactivate Cryptosporidium. Only chlorine dioxide tablets (like Potable Aqua Chlorine Dioxide) are rated for Crypto, and even then they require a 4-hour contact time. If Crypto is a real risk, specialist outdoor publishers recommend pairing tablets with a filter.