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I've used these many times before, always followed the instructions (3 tablets/Liter, shake, wait 30 minutes minimum) and never had (or noticed) any issues. I've always been under the impression, that second to boiling it was the most effective method of purification.

However, A few weeks ago I hiked a few days on the AT using iodine tablets as my primary method of purification. When I got home, I forgot about the water in my camel pack for a couple weeks. When I finally went to clean my camel pack looked like I was raising sea monkey's in there.

Has anyone had the same experience? Could it be the quality of the tablet? I'm well aware that even the best polymers aren't impermeable on an extended timeline, but this was only a few weeks, and whatever it was, there was a lot of it.

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    "...of purification" - no, Sir, it does not. It doesn't purify anything. Arguably, you are soiling it even more, with iodine. But it is sterilizing ;-)
    – Stian
    Commented Nov 8, 2019 at 8:24
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    I suppose you are correct but at this point you are getting into the weeds of the definition of purity, which is somewhat ambiguously defined anyway.
    – mreff555
    Commented Nov 8, 2019 at 14:49
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    @mreff555 The distinction is really important to understand, and isn't really in the woods. Iodine protects you from microorganisms, but would do nothing for toxins
    – Carl Kevinson
    Commented Nov 8, 2019 at 15:41

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Welcome back to good old chemistry class! Apologies if this gives you nightmares.

First, the tablets used for water purification are not elemental iodine, but a crystal form called Tetraglycine Hydroperiodide. So there are things besides simple iodine getting into your water. More importantly however, is that many of these things, including the iodine itself, are not soluable in water, or only partially so. (See the wikipedia article on iodine) Instead, the iodine mixes with the water giving it time to permeate the cellular membranes of the organisms also floating around, thus killing them.

Your water has sat warm and stagnant for a time, allowing the iodine and other impurities to form precipitates. The things you referred to as Sea Monkeys, I assume are little dark orange to black colored blobs. These are nothing but clumps of precipitated iodine.

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    Great answer. You are correct, they were mostly black blobs.
    – mreff555
    Commented Nov 7, 2019 at 17:47
  • Is is the water still safe to drink?
    – nitzel
    Commented Nov 8, 2019 at 14:16
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    I would assume it would be, but you would probably want to filter or strain it since the precipitate wasn't settling on it's own.
    – mreff555
    Commented Nov 8, 2019 at 14:50
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    @nitzel - That sounds like a nice new question, perhaps to ask at the Chemistry SE.
    – cobaltduck
    Commented Nov 8, 2019 at 17:49

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