DWC cannabis – safe Dissolved Oxygen Saturation range throughout months of the grow period

Does anyone have any idea about DO Saturation range to insure optimal root ball and microorganism colony oxygenation?
What the optimal sustained dissolved oxygen saturation range that insures healthy plants and excellent “bennies” microbial oxygenation?
What DO saturation is considered “low oxygen” inviting fungal outbreaks and infestations ?

@Hammer @Dumme

Hey @JH231 if your growing in a DWC your water temp is more important then your D.O. in that when the temp of your water rises your D.O. decrees . A good air stone will give you plenty of D.O. if you can keep your water temp between 62 to 70 degrees the cooler water holds oxygen longer then warmer water. You really don’t want your water temp above mid 70’s for to long as this invites root rot. Hope this help with your question and happy growing. :cactus:


Some additional information, about 68F-72F is the sweet spot for dissolved oxygen in the water. Below 68 biological cellular activity slows and can slow nutrient uptake and growth in the plant, and above 72*F will drop O2 levels enough that root rot might set in in the reservoir.

A DO level of at least 4 ppm is needed to keep things relatively healthy for a lot of plants. Usually the level should be maintained at 8 ppm(7-10, no advantage at higher – to say 20 ppm).



Tee, Thanks for responding, but my questions are about actual real time measured DO % Saturation values in vivo.
I have seen the DO charts and heard the water chiller salesmen pitch, but neither the DO charts nor the chiller salesmen have answer to these questions. The questions have nothing to do with DO charts predictions nor water temperature. These are real numbers derived from DO testing and the % DO saturation changes in relationship to the collective oxygen demand required by the plants and microorganisms.
My questions are clear and straight forward:
Does anyone have any idea about DO Saturation range to insure optimal root ball and microorganism colony oxygenation?
What the optimal sustained dissolved oxygen saturation range that insures healthy plants and good microbial oxygenation?
What DO saturation is considered “low oxygen” inviting fungal outbreaks?


I actually did answer your question above.



mac, you missed the point again… I’m really not interested in ppm DO concentration. The questions are about DO % Saturation something very different. Are you familiar with DO % Sat?

What do you mean? You end up with same result in DO in the water.

BTW, if you can’t keep reservoir temps this low, it is really hard to keep DO levels high enough.

For example, in ocean water, the salt is a good analog for our nutrient salts in a hydro reservoir, at about 77-78 degrees Fahrenheit, the O2 levels drop to 7ppm, but this in open ocean near the surface, with lots of movement and surface area to absorb O2 from the air, not to mention how much seaweed and other aquatic plant life floating in the ocean add to the water.

It would rapidly drop lower with a voracious plant’s root consuming much of the O2 without putting anything back into the water.

And at about 60F the O2 is at about 8.4ppm.

The point is temperature does directly effect the DO levels.

However with tons of aeration you can make temps up to near 78F work, but we are talking a whole lot of aeration and almost to the point it almost becomes like aeroponics, lol. Almost more air than water and a misting of the roots. I personally have made 78F work for me when I had no other choice in DWC.

Maybe if you explain more I will be able to understand what you mean differently by saturation as opposed to concentration. I don’t really see a difference, not even by technical definitions.



I mean you could say the water is saturated with 8ppm of O2, or you could say the water has a 8ppm concentration of O2 in it, it basically is the same thing.

As I also said above, you can force more O2 into the water at higher temps, it just becomes harder the higher the temps get.

Either way, about 8ppm, if possible, is what you want to shoot for, regardless of temperature.



In what way are you planning to measure this DO% Saturation. As far as I know the only devices measure in PPM, and otherwise I don’t think anyone can determine % without any of these tools, even if there is a tool that will measure % specifically as opposed to ppm, you still need the tool.

Something else to consider, just an FYI, the more concentrated the nutrient salts in ppm in your water, also the harder the water has of dissolving O2. For example my above statement using sea water as an example, it is just that, salt water. The relative dissolved O2 in it would be much higher at the same temps in fresh water with a very low ppm. So another way to help increase O2 in your reservoir would be to keep your nutrient at a lower ppm solution.

I find even a ppm of 600 or lower, maybe as low as 400 ppm of nutrients will work just as good in DWC, especially if temps are controlled at about 70*F, and as highly oxygenated solutions help with nutrient uptake at the roots.



I had another thought, if you mean you are looking for 100% saturation, then yeah, for example, at 77*F, under most conditions, 7ppm would be 100% saturation at that temp in ocean water, all things being equal.

But again, I can’t help much more than that unless you elaborate more on your idea of saturation.

And I did poke around researching on the net to try and see if I could find anything that would point me in another direction, maybe more to what you are talking about, but I came up empty, all I could find was DO in ppm.

happy growing,



Seems to me you answered the question in terms which all reading would find very simple to understand more air temps can be higher less air temps should be lower pretty simple to me. Perhaps this question is more related to the HHO generator type units some people are selling for hydroponics not simple air stones and pumps that experienced growers have used for years with success or the fact that in that time we’ve learnt the value of temp control and simplicity (if it works don’t over think it)
Seems more to me that this question was a trap for a debate than anything else?


Well we’ll see if @JH231 does indeed come back and debate.

But I suspect as no one else seems to have answered this question differently and JH231 hasn’t come back to explain further, maybe he, himself, was a little confused on the idea of O2 saturation.

And again, he is more than welcome to better explain what he means so we can help him better as to what he is looking for.

But thanks for the support @Donaldj

happy growing and oxygen saturating everybody :smiley:



Mac, no disrespect intended, but it’s clear that DO% Saturation is something really new for you and your absolutely correct, a tool to measure the DO % Saturation is absolutely necessary to test and measure DO % Saturation. Without the tool, there is only hope and hope. When hope fails and roots suffocate, die, decay, you can expect the dreaded fungal outbreak because that is predictable.

What do you think is more important when it comes to sustained minimal safe oxygenation for 2-25 mature DWC cannabis plants and 2 pounds of beneficial microbial colonies, 8-9 ppm DO or 100% DO Saturation or thinking out of the box - what about 12-15 ppm DO concentration @ 100% DO Saturation and 5 pounds of microbial colony?

DO % Saturation - The standard unit of oxygen saturation is percent (%). In aquatic environments, oxygen saturation is a ratio of the concentration of dissolved oxygen (O2) in the water to the maximum amount of oxygen that will dissolve in the water at that temperature and pressure under stable equilibrium.

Oxygen saturation is a relative measure of the amount of oxygen that is dissolved or carried in a given medium. It can be measured with a dissolved oxygen probe such as an oxygen sensor or an optode in liquid media, usually water.

DO Concentration (PPM DO or mg/Liter) – Dissolved Oxygen is the amount of gaseous oxygen (O2) dissolved in the water.

DO concentration can be measured by colorimetric methods, a sensor and meter or by titration. The colorimetric method offers a basic approximation of dissolved oxygen concentrations in a sample. … The traditional method is the Winkler titration.

Many things affect the DO Concentration (PPM or mg/L) and DO % Saturation (20% Sat, 50% Sat, 90% Sat, 110% Sat, 140% Sat and so on… fractional concentration of oxygen, barometric pressure, partial pressure of oxygen, water temp, salinity concentration or solute concentration and the oxygen demand of plants and animals consuming dissolved oxygen living in the water.

**“BTW, if you can’t keep reservoir temps this low, it is really hard to keep DO levels high enough_**_.” IF sounds like hope… What DO Sat is high enough, safe, constantly sustainable for months of the growing season?

Eliminating “IF” and “hope” of sustaining safe oxygenation continuously without low oxygen insults is not possible when you limit yourself with air, DO Charts and water chillers until you can think out of the box and use Henry’s Law - In chemistry, Henry’s law is one of the gas laws formulated by the English chemist William Henry, who studied the topic in the early 19th century. … In other words, the amount of dissolved gas (oxygen O2) is proportional to its partial pressure in the gas phase. The proportionality factor is called the Henry’s law constant.

Pro football players, doctors, nurses, EMT’s, fighter pilots, welders and plumbers, SCUBA divers, jewelers all apply this Law every day to exceed the exceed the oxygenating limitations of air. There are many occasions when air simply is not capable of satisfactory oxygenation. Air is mostly Nitrogen gas. That’s why hospitals use oxygen vs. big electric fans.

Manipulating DO Concentration to insure 100% DO Saturation – air is seriously limited when it comes to minimal sustained safe oxygenation for months in DWC.
If plenty of air, chilled res water would really insure minimal safe oxygenation continuously for months, there would be no low oxygen insults, root balls and microbial colonies would be healthy. Low oxygen events, suffocation and death and decay would not offer opportunity for fungal feasts. Prevent the fungal outbreak and insuring healthy eco systems seems more positive than waiting for the outbreak and trying to kill the fungi and save sick and dying plants.

Many growers claim they never have worries or problems with fungal outbreaks. Do fungal outbreaks concern you, are you into preventing fungal outbreaks by insuring minimal safe oxygenation continuously or treating outbreak aft they happen?
The difference between DO Concentration and DO % Saturation are simply 2 different ways to evaluate dissolved oxygen in water.

I still have the same 3 initial questions:
Does anyone have any idea about DO Saturation range to insure optimal root ball and microorganism colony oxygenation?

What the optimal sustained dissolved oxygen saturation range that insures healthy plants and excellent “bennies” microbial oxygenation?

What DO saturation is considered “low oxygen” inviting fungal outbreaks and infestations?


Seems I am just a simple grower and ignorant to the science at play likely due to the fact that I am not a chemist scuba diver or welder also not growing inside a pressure chamber? I am hoping I don’t have to buy another damn meter at this point or reinvent the wheel? to me I keep things simple as possible pumps not air tanks which does the trick lots and lots of fine air bubbles I use hydro specific nutrients frequent changes and enzymes to keep my roots healthy. I enjoy learning new things when it comes to growing but not at excess cost for minimal gain and have very rarely had root issues not directly related to failure to monitor ppm of nutrients properly or notice a pinched airline?
I assume you are doing this research for a purpose otherwise Murphy’s law would suffice being a drunken Irishman with infinite wisdom if it isn’t broke don’t fix it comes to mind? I may be rusty on my chemistry but isn’t O2 a oxidizer and actually extremely dangerous and corrosive by nature H2O2 is commonly used in DWC to aide in bacterial control and keep systems clean but applies to the principle of free O2 molecule attaching and attacking bacteria .
I personally wouldn’t want to add O2 to a grow space with so many potential fire hazards ignition sources and damned if I need another pump to create a vac/pressure chamber in my grow room?


No actually it is not.

This is basically the same thing I said here:

7-10 ppm saturation would be the recommended number, and it would be at 100% saturation, if this is the the maximum amount of oxygen that will dissolve in the water at that temperature, nutrient concentration, and pressure under stable equilibrium.

Maybe you could do as low as 4ppm as I also said above, if that is the maximum saturation level you can achieve at the temperature, nutrient concentration and pressure in your environment.

Also there is no advantage higher than about 8ppm, as I already said above.

And yes I basically already said this as well above, this is why I mentioned nutrient salts and salt water. And of course I did mention temperature.

As I said, at higher temps, you can kind of “force” higher Do saturation levels with more aeration, this would be very short term due to temps being higher, but as the air stones supplying air is right near the roots, it would keep it high enough, long enough, for the roots and microbes to benefit.

With a pure O2 injection, you could also manipulate the O2 levels at higher temps in the same manner if directly near the root ball and its contained microbes, yes, but very likely much higher temps than 78*F would still cause problems, as also stated above.

Again, no matter how you look at it, 4ppm at 100% saturation is probably the least you can get away with and about 8ppm is optimal with no benefit any higher.

7-10 ppm would be the optimum saturation range, as was stated above.

And lower than 4ppm and you are likely going to have problems, this would likely invite root death and fungal problems.

I mean 4ppm O2 is 4ppm O2 and same for 8ppm O2, regardless of if it came from natural air or concentrated pure O2 injection.

None of what you stated above changes any of this, I am not trying be argumentative or ignore the concerns or ideas above, but the numbers stay the same.

I think you are making it a little more complicated than it needs to be.



Don, this is clearly not for you, you don’t need a meter nor reinvent the wheel or revise the the concept of zero -0-. I understand your point of view and appreciate you sharing that view.
Thanks for you opinions.

Also, if at 77*F, 7ppm is 100% saturation, then at the same temp, salinity and pressure, would not 10 ppm be about 140% saturation?

The ppm number stays the same regardless of the saturation percentage.

If I am still not understanding you, I am more than happy to be corrected and further informed. I am always an active learner and am always willing to learn new things.

Try and keep your points a little shorter and more directly to what you are looking for. I did read the entirety of the above, but it didn’t seem to make any changes as to what you are looking for, at least not as far as I could tell. I mean I am already familiar with Henry’s law in chemistry.


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Just read what you want and leave the rest. That’s fine.

Pure fresh water, no plants or microbes consuming any O2, salinity -0-, @ 77F, 8.4 PPM DO concentration. DO % Sat 100%. When you subtract the oxygen consumption used by the plants and microbes – subtract for the additional salinity, the DO concentration PPM and O2 % Sat will drop considerably lower in that 77F water.

The greater the collective oxygen demand of the plants and microbe and the greater the salinity… the lower the DO concentration and SDO Saturation falls. This brings back to the 3 questions I began with.

The DO Charts many are familiar with and cite do not compensate for any aerobic life consuming O2 in the water.

Pure fresh water with nothing aerobic in the water consuming O2 will be: 84F 7.8 PPM DO, 100% DO Saturation.

I have noticed that the DO Charts (predictions) as the water temperature changes the DO Concentration PPM also changes, but the DO % Saturation always reads 100% Saturation regardless of the water temperature or the PPM DO Concentration… chilling water to achieve a target the target 100% DO Saturation may be the point of chilling the water temperature.

60F water – 10 ppm DO – 100% DO Sat — @ 4 ppm DO — 40% DO Sat (less aerobic O2 consumption and salinity concentration will be < 40% DO Sat)

65F water – 9.1 ppm DO – 100% DO Sat — @ 4 ppm DO – 44% DO Sat (less total aerobic O2 consumption and salinity concentration will be < 44% DO Sat)

70F water – 8.9 ppm DO – 100% DO Sat — @ 4 ppm DO – 45% DO Sat (less total aerobic O2 consumption will be < 45% DO Sat)

86F water – 7.7 PPM DO – 100% DO Sat — @ 4 ppm DO – 52% DO Sat (less total aerobic O2 consumption will be < 40% DO Sat)

The DO Chart, 100% DO Saturation is constant while the water temp and DO Concentration PPM change. That demonstrated why the oxygenating capabilities of air is so limited regardless whether you double, triple or quadruple the volume of air… the % oxygen in air will be the same… enter Henry’s Law (partial pressure of an individual gas (O2) within mixture of different gases).

Glad you have a working knowledge of Henry’s Law. Henry’s Law is all about gas solubility in water and how oxygen solubility in water can be manipulated with gas partial pressure and gas concentration at constant 1 ATM pressure (14.7 PSI).

I think the application of basic water and gas chemistry can greatly enhance crop productivity, grow out time and crop quality when applied. DO is easy to manipulate when you have a goal in mind… but few seem to have a scientific grip on the optimal DO Sat goal is. I do understand that growing a few plants for fun is not the same growing super high quality buds for sales and high profits.

Thanks for participating and sharing your ideas with me mac.

New to these forums but it seems I’ve found a good one. As a fish farmer I read DO in mg/L and can manipulate levels from 0-40 on a microbubbler and tank from a cutting torch. When I ran liquid o2 we would mix in 80mg/L to maintain good saturation for the fish. My questions:
What experiments have you conducted with plants in hydro. You stated 4ppm is sufficient but levels in the 7-8 range are max. Typically with trout at 55deg water I try to maintain 7mg/L min and 10mg/L max so it sounds similar but we have been known to run up to 12-14 in transport which gives them a boost, kind of like athletes during a workout…can plants benefit from this?

Also fish can get oxygen narcosis if put into over saturated water more in the 18mg/L and up range, have you ever experienced similar experiences in the hydroponic world?

Concerning temps, I can easily reach 7mg/L in 85deg water but most have difficulty at 70 in hydro so they keep it cooler. What would be the max temp even with good o2 saturation that plants could flourish in? Is there a plateau where they start to loose performance?

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