@ Colin, who wrote, "Ben,
It's true that cysts are resistant to chlorine (ie, bleach) but it is NOT chlorine that kills them when using chlorine dioxide despite the name. It may take 4 hours to do so in certain conditions, but ClO2 will get them.
I am curious as to what other critters Colin is referring. I've not read anything along those lines."
Colin -- just to be clear -- I was referring to chlorine - as in common household bleach -- not CLO2. Bleach is cheap as heck whereas CLO2 is expensive. While the latter is effective against cysts, the treatment time can take hours -- which is impractical unless treating water overnight. Much better, IMO, is to simply use chlorine -- to kill the tiny stuff -- and rely on a simple filter like the Frontier Pro to trap the bigger stuff (like cysts). The combo can cut way down on treatment time.