I stand 100% behind what I wrote. One cell critters are hard to kill. 1000% as difficult as bacteria. I found this out in S.E Asia. No chlorine, period. Iodine. And iodine is ghastly to the taste buds. For zero taste of amoeba and protozoa it means O3 treatment for sterilization. Or better yet, lab verification. How you sterilize your water depends 101% on where you live.
I got infected with one cell protozoa eating SE Asian seafood. Nothing touched it even at 300% dosage. I finally got rid of it after I was dosed with Diodoxine. At risk of optic nerve destruction. This is a tough way to learn the basics. Our local purification plant follows Mex govt instructions .5 micron + R/O filters and UV sterilization. I am going to look for a plant with O3 sterilization.