What happens to salt water in a jug?

<a href=showthread.php?s=&postid=10507971#post10507971 target=_blank>Originally posted</a> by crumbletop
I have not noticed any film on my RO/DI reservoir or any residue. I don't store salt water very long so I can't say I've noticed anything either way with that. It is very odd that you have RO/DI growing stuff. That suggests a dirty container and/or some sort of ongoing supply of nutrient/substrate. My hands never get into my container, so I'm pretty sure I don't add anything. I have had a continuous water presence in the reservoir for about 1.5 years now.

Even though RO/DI has ) TDS, it is FAR from clean of bacteria and/or substrates. This is why people (like myself) who grow bacteria for a living either autoclave RO/DI before use in cell culture or pay $10+ per pint for sterile nuclease free water. Next time I come to your place, we can streak some of your RODI on an agar plate and I am sure you will be suprised as to what starts to grow.
 
<a href=showthread.php?s=&postid=10508662#post10508662 target=_blank>Originally posted</a> by c_stowers
Even though RO/DI has ) TDS, it is FAR from clean of bacteria and/or substrates. This is why people (like myself) who grow bacteria for a living either autoclave RO/DI before use in cell culture or pay $10+ per pint for sterile nuclease free water. Next time I come to your place, we can streak some of your RODI on an agar plate and I am sure you will be suprised as to what starts to grow.

I don't dispute that it may have bacteria around -- I just don't think the bacteria has anything to grow on.
 
<a href=showthread.php?s=&postid=10507704#post10507704 target=_blank>Originally posted</a> by c_stowers
I will have to disagree with Randy on this one (even though I highly respect his opinion). I've noticed that even RODI grows bacteria if left stored for >2 weeks. This is apparent from the biofilm that accumulates on the surface, but is most noticable on the sides of the container it is stored within. I have noticed the same thing in stored SW. Maybe this bacteria has no effect, but I doubt so. The bacteria must be growing on something, and thus depleting some of the constituents of synthetic sea salt. Also, bacteria condition their media, typically to very low Ph. Thus, as they grow, they will lower the pH of the saltwater by re-buffering it themselves.

That's a good point, Chris. I have growth on my RO tubs (have to vinegar them out about every two weeks or so-there is always water in them). That didn't even click when I posted above (week 2 of bronchitis addled brain...). Cycled water would be worse, but I have had slimy growths on my Rubbermaid tubs from RO/DI and mixing salt water.
 
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