"Stuff" will only grow in the bottles if they are opened and left to sit for a long period of time. Bottles that have never been opened except for their initial filling should still be fine. I'm basing this on my own experience with this product. Storing the product in different environments may introduce variables that i myself never ran into. As such, pouring it into another clean container to inspect might be a good idea if someone has some old fluid that they want to donate to someone else and / or make use of themselves. Sean
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