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Dissolved oxygen for DWC, what’s do those DO meter test numbers really mean?

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Most hobby DWC pot growers say you must have plenty dissolved oxygen in the res water all the time or the roots and microbes die and fungus takes over.

I have a new DO Meter:

 What test numbers on a DO Meter mean “low dissolved oxygen?”

What numbers mean “too much dissolved oxygen?”

And what numbers mead you have “plenty dissolved oxygen”


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High Jack


Isn't there some kind of owners manual for it?  What's the make and model and I'll look it up for you.  I'm a retired chemist and worked with a lot of that kind of equipment so should be able to figure out what's what.


I just keep airstones going all the time under the plants and that seems to be enough O2.  I even bubble my RO water that I use on my potted plants.  Would be nice to have one of those to be able to see what difference that makes if any.




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Thanks for responding Rat, I have a YSI 550-A DO Meter, the operation manual came with it. It’s easy to operate, a great instrument, but the meter manual does not say anything about the questions I ask in this thread about these DO ranges for hydroponic pot res water.


Last summer, I ask a water chiller salesman these same questions and he basically told I needed a water chiller, "chill your res water and there will be 'plenty oxygen” and no need for a DO Meter. He told me a thermometer will basically do the same thing as a DO Meter. I don’t think he had a clue, but he was a classic water chiller salesmen and had his sales pitch memorized well, he had it down and didn’t miss a beat in his pitch.


-- but I really want the benefits of higher metabolism, maintaining  res water temp in the low 80's F, not in the 60's.


I bought this YSI meter so I can predict any low oxygen developments early and correct the low O2  before roots die and fungal infection sets in, I'm not interested in prevention vs. rotting roots, crisis intervention and the race for the cure. Been there, done that and know that low oxygen insults always negatively affect plant and microbial health even if you are lucky enough to salvage some of the crop. Although most DWC hobbyist say the never have fungal outbreak some of us do... treatment and attempt at the "cure"  is a mess to deal with.

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It’s April now, res water temp constant @ 81F, room air temp 72F, DO Sat. constant @ 100% - 105%, root growth great and healthy, no fungi, bennies prolific, everything looking lovely.

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