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Jack434

What happened to all that O2 dissolved oxygen (DO) in RDWC canna-grows?

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Would appreciate 2nd and 3rd opinions please from experienced hydro canna-growers about this. Guessing and bro-science appreciated too.

The internet dissolved oxygen chart says @ sea level, 79F fresh water, my reservoir water DO will be 8.2 PPM DO and 100% DO Saturation… air pump humming like a champ vibrating the floor and 4 bubblers are frothing the water.

I have ask and been told by some hydroponic forum gurus that this DO Concentration/DO Saturation is considered “plenty oxygen” like Perfect Oxygenation. Through actual DO testing, I have discovered over the last year that the internet DO Chart is no more than a DO prediction which is often very different than an actual real time DO test result. I am shocked a so much difference.

I tested water with a DO meter and found the actual DO test results to be dramatically different than the predicted DO with the DO Chart. The tested DO in 79 F water was actually 4.1 PPM DO and 50% DO Saturation. This is great dissolved oxygen levels if you are growing hydroponic lettuce and tomatoes.

What in the world does this 50% difference in the DO Chart predicted vs. actual tested / confirmed DO Conc. / DO Sat. really mean?  My guru buddy says, “50% DO Saturation and 4.1 PPM DO Concentration is definitely considered low-oxygen in a RDWC canna-grow and the oxygen most probably evaporated, like water evaporates.”

Why is there so much difference between the predicted DO chart values and the real tested DO values?

What could have happened to half of that dissolved oxygen in the reservoir water?

I have heard and read about the negative effects of low-oxygen problems negatively affecting (suffocating) roots and Benny health, sick roots and sick Bennies, suffocation, root rot = one stinking, slimy, decaying mess that can happen overnight.

She suggest, “buy a larger air pump (buy a quiet air pump) and several more new air bubblers… bubbling more air = bubbling more oxygen… low-oxygen problem will go away, roots and Benny’s will be healthier and crop more productive if not suffocating.”

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I've never measured the DO in my DWC tubs but they grow fine.  I use 2 - 12" airstones now where I used to just use one and don't notice any difference.  I keep the temps around 65F so there should be higher levels of DO than at 79F.

 

The finer the bubbles the better the saturation is going to be as well.

 

:peace:

 

 

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They say that fine bubbles are better than giant bubbles for some reason. If you are into really small bubbles you might consider Nano-bubbles produced with a Nano-bubble generator. These little dudes are really impressive… they make fine bubbles look like a basketball comparatively.

A major problem with all fine bubble stones as you know, they stop-up often because the pores are small and those little pores are impossible to clean well. Those bubblers are basically disposable but the do work well before they stop-up.

Have you ever seen or read this by chance? Understanding Dissolved Oxygen by Kurt Becker 2/27/2017 http://www.ballpublishing.com/GrowerTalks/ViewArticle.aspx?articleid=22058

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That link won't open for me but I've read enough about the subject to know that what I'm doing works so don't concern myself with it much.

 

I'm just using those cheap blue aquarium 12" stones and they generally last two or three grows as long as my nutes stay clear so for $10/pair I just replace them if needed.  When they plug up they don't seem to be able to be cleaned and reused.  I've tried caustic soda, bleach straight out of the bottle, 35% hydrogen peroxide and strong sulphuric acid to no avail.  I wonder if that CLR stuff for Calcium, Lime and Rust would do anything. :)

 

1 hour ago, Jack434 said:

They say that fine bubbles are better than giant bubbles for some reason.

 

The reason is that the smaller you divide something the higher your surface area for a set volume.  The higher the surface area the more of it that is exposed to be able to dissolve in the water.

 

Think of something the size of a sugar cube that's one centimeter square.  6 sides so you have 6 square cm of surface area.  Cut that cube into 4 equally sized cubes of 0.5cm square.  Now you have 4 cubes of (0.5cm x 6 sides x 4 cubes) = 12 square cm of surface area exposed or twice as much.  Keep doing that and the surface area keeps getting larger.  Now if that original sugar cube was a solid block of sugar instead of sugar crystals pressed into a square how much longer would it take to dissolve into a cup of coffee compared to the same amount of sugar already made into the tiny crystals before adding to the coffee?  A lot longer.

 

The same kind of surface area math works with round bubbles of air as well.

 

:peace:

 

 

 

 

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