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


According to some recent research done by my good buddy @Niala, here is what he found in regards to your questions as posted in a recent thread in Robert’s Lab forum bergmanslab.com where we have been discussing o2 saturation and different devices and methods of increasing dissolved O2:

Roots plant love supersaturated dissolved oxygen and you can push it too around 16mg/L according to some source :


I did not find any limitation except pass a certain point, you’ll have to increase the air pressure, Henry’s law oblige, if you attent to go further …:wink: At sea level, the maximum you can reach in supersaturated DO it’s around 18 and 20 mg/L

However, be conscient that supersaturated dissolved oxygen in water is gone a be tough on every metal parts that will came in contact with it.

Also, if plant love it, that means all plants love it, including algae… So, in a supersaturated oxygen environnement, algae can be a problem (pythium) if you have temps issues…

Anyway, roots system are plenty happy if you maintain the DO between 8.2 and 9.7 of what I can found in my research in Internet and the graph from my previous post … :wink: :innocent:

Hope that’s respond to your question @tdubwilly1979

~Al :v: :innocent:



Thanks Hashtag – Your fish farming input to this thread is appreciated. Intensive recirculating fish farming and canna-hydroponic horticulture (DWC and RDWC) are both very similar when it comes to requirements that will insure optimal water quality, specifically dissolved oxygen requirements 24/7.

Do you think that a super air compressor or 2 air compressors would pump plenty oxygen through 1 or 2 $10.00 bubble stones 24/7 for months to harvest or no? Do you think an air compressors would provide plenty dissolved oxygen for a recirculating intensive fish farmers’ fish tank that is chock full of mature market fish and many pounds of large colonies of beneficial nitrifying bacteria microbial colonies?

One gallon of Nitrobacter microbes weighs 8 lbs. One gallon of The Bacillus Amyloliquefaciens in Hydroguard also weighs 8 lbs. One gallon of fresh water also weighs 8 lbs. Five gallons of these live microbes demands 5 times more DO than 1 gallon of microbes. More microbial mass plus more canna-roots mass during months of a growing cycle always require more and more DO to be healthy as the aerobic microbes grow and mature in an aquatic life support system.

After a few google searches (intensive recirculating fish farming oxygenation practices) that when it comes to oxygenation, commercial r-intensive fish farmers are at least 50 years ahead of commercial hydroponic canna-growers in the oxygenation arena. Both farmers are balancing dual symbiotic aerobic ecosystem within am aquatic life support system. One farmer implementing and manipulating DO concentrations to achieve greater success, the other chilling water always, guessing and hoping for plenty dissolved oxygen but seldom can ever achieving even close to the optimal DO concentrations, i.e. 16 PPM DO.

Success means producing the healthiest product possible as quickly as possible. Gorilla farmers growing Mexican dirt-weed are also successful growers… success is relative and very subjective for hobbyist growing for a jingle vs. growing for pharmaceutical quality and commercial quantities. Preventing suffocation within the life support system by simply insuring optimal safe DO levels continuously to harvest.

Regarding DO Concentration and DO Saturation: If a “fish can get oxygen narcosis if put into over saturated water more in the 18mg/L and up range,”
In your opinion, what is your point of using such high DO supersaturation? I.E. generating 40 PPM DO with compressed oxygen or 80 mg/l DO supersaturation with liquid oxygen? I cannot think of any valid reason to generate such high DO supersaturation like this knowing high DO supersaturations like this will intentionally cause a serious toxic oxygen water quality problem. I find no relationship of hyperbaric oxygen narcosis in intensive fish farming.

Thanks for joining in the conversation. A conversation about the most vital element in hydroponic canna-grows that may be interesting and informative to a few and totally meaningless fodder to most.


Hello Al,
First, thanks for your interest, efforts and time, especially providing Biksa’s oxygenation piece.
Some general observations a year down the road:
Hashtag, a real fish farmer, is no doubt an expert when it comes to manipulating DO concentrations to achieve optimum safe oxygenation for his fish; he grows fish commercially for his living. He knows how to manipulate O2 tensions in fish tanks full of fish and nitrifying bacteria colonies by manipulating O2 tensions in Henry’s Law. He’s basically a real DO water quality expert.
He makes the DO in his fish tanks anything he chooses, 4 PPM DO, 10 PPM DO, 16 PPM, 20 PPM, 40 PPM, 80 PPM concentration, DO saturated, DO Supersaturated in fish tank water. He simply increase the ambient air O2 tension > 159 mm/hg to say 200 mm/hg or more which would automatically decreases the Nitrogen gas tension in air. He’s a wizard at manipulating DO in water without buying a water chiller and using cold water… behold a real wizard a DO wizard.

He grows and sells fish for a living and I’m sure he sells a pound of fish is far cheaper than a commercial canna-grower sells pound of his commercial pharmaceutical quality canna-buds.
He increases and maintains optimal DO concentrations and saturations continuously in his life support fish tanks insuring no low DO events for both his eco-system in his fish tanks. However he accomplished this magic, his continuous DO production must be cost effective per pound of fish he produces and sells at market price. He also knows that low O2 insults seriously harm his crop of fish which directly affects his income and families life style
I spent a few hours researching intensive fish farming techniques, specifically water quality and ideal dissolved oxygen requirements. I discovered that fish farmers do manipulate DO concentrations dramatically which is SOP, intensive recirculating fish farmers do this every day worldwide. This is not bro-science, this is steeped in aquaculture science, it’s common practice, common knowledge in the intensive fish farming industry and has been around for decades.
I read the article you posted, interesting. The nut of this oxygenation piece: “Once the pore spaces become depleted of O2 for a period and then coupled with warmer temperatures, rots and diminished uptake are sure to follow. Even though your plants aren’t showing root rot, it doesn’t mean that they are wasting a lot of their valuable energy fighting infections at the roots rather than growing faster; all simply due to a lower O2 level at the roots.”
The DO (elemental O2) is the common denominator that determines various degrees of what each grower considers and calls “success.” “Success” for most hobbyist is often defined by no more than pics of plants and growing a plant that contains enough THC to alter ones state of mind when buds and leaves are consumed. “To each his own,” so they say.
Licensed commercial pharmaceutical growers may grow crops for the cannabinoid canabadiol (CBD) purity/concentrations. Either way, for the commercial pharmacudical or hobby growers, the optimal health of the plant throughout the growing season is directly proportional to the health of the plant roots, Benny’s, ATP production and metabolism that are living within any hydroponic life support system.
The perception of success is important, but relative for every canna farming hobbyist. Even the gorilla farmer that plants a sack of canna-seeds in a National Forest or a Mexican desert and returns 9 months later to harvest and behold what he has grown is considered to be a relatively successful farmer if when only few seeds sprout and grow to near maturity.

The article: Dissolved Oxygen in Hydroponics, “Dissolved Oxygen in Hydroponics is that missing link to faster growth rates, healthier plants and even bigger yields.” Written by Erik Biksa - Erik is a co-founder of Grozine and the editor at Grozine Hydroponics Magazine.

No disrespect intended toward the writer, he writes for a living. His oxygenation infomercial begins setting the stage with the image of a water chiller with this ambiguous open ended caption: “A Chiller increases Dissolved Oxygen in Hydroponics for faster growth and healthier crops.” This writer recommends classic archaic mechanical aeration methods coupled with hypothermia to insure minimal safe oxygenation.

This oxygenation (DO) technique is always limited and seriously restricted by Mother Nature’s natural boundaries’ (Chemistry Laws), i.e. ambient air, O2 gas tension in ambient air and cold reservoir water temperature, water salinity, total aerobic biological oxygen demand (BOD) and so on…

But, ambient air is usually called/written as oxygen (elemental O2) and often considered to be – “FREE.” “Cheap” is only 1 click up from FREE… Free often trumps cheap if and when you’re on a recreational hobby grower’s budget which is understandable.

The writer has many factual references, but emphasizes that marginal DO control is achieved by chilling the reservoir water, hypothermia. The effect of hypothermia – the DO Concentration changes slightly more than 1.00 PPM for every 10 F change in water temperature… that is only 1/1,000,000.00 PPM.

“SO, where’s one of the easiest places to get more performance out of any combustion engine that also happens to be one of the most overlooked performance factors in most gardens?”

“Dissolved Oxygen in Hydroponics is that missing link to faster growth rates, healthier plants and even bigger yields.” “However, few “think O2” when contemplating what is propelling their garden forward in the hopes of achieving health yields.” [the article suggest that minimal safe oxygenation is dependent on water chillers, cold reservoir water, more ambient air and more air bubblers that are functional, new and not stopped up.]

Fact: “Just like in humans, O2 is critical for respiration-when plants actually use all the sugars they manufacture during light hours to grow, this mostly happens during the dark cycle. You can load your crops with carbs, but if they don’t have enough O2, that can become a limiting factor in how much of those carbs they can “burn” for growth. Oxygen availability in the root zone is highly critical for root health and nutrient uptake. In warm and wet conditions, oxygen levels are low because colder water holds much, much more water oxygen-as do the pore spaces around the roots when empty.”

Fact: “Once the pore spaces become depleted of O2 for a period and then coupled with warmer temperatures, rots and diminished uptake are sure to follow. Even though your plants aren’t showing root rot, it doesn’t mean that they are wasting a lot of their valuable energy fighting infections at the roots rather than growing faster; all simply due to a lower O2 level at the roots.”

*** “Typically 16 PPM (parts per million) of DO (dissolved oxygen) at the roots is considered very good.”

“Most healthy growing situations are probably half of that [or only 8 PPM DO concentration]. Double these amounts are possible with specialized technologies that actually dissolve O2 in solutions, rather than just bubble it through (diffusion).”

This hydroponic oxygenation piece is interesting and does contain a few important scientifically accurate facts, but the writer seriously limits his oxygenation recommendations when he fixates and promotes DO dependency bases solely on water chillers, cold water, hypothermia, 65 F water temperature, mechanical aeration, *ambient air and DO chart predictions. Ambient air O2 tension, water temperature and biological oxygen demand (BOD) being the limiting factors of dissolved oxygenation aquatic life support systems, i.e. intensive recirculating fish farming, aquaponics and hydroponic DWC, RDWC canna-life support systems.

At best with no aerobic plant roots or beneficial microbes in that water, ½ of the optimal 16 PPM DO is not available. That’s a 50% below optimal DO concentration in the water before any canna roots or aerobic Benny’s are added to the water in the hydroponic life support system. When the “grow” contains mature plants and mature microbial colonies ½ of that 8 PPM DO is consumed by the dual eco systems.

The biological oxygen consumption reduces the DO to <4 PPM DO considered a low oxygen crisis for fish and canna-culture.

In order for this writer to achieve the ideal or optimum DO concentration (16 PPM DO Concentration for a hydroponic canna-grow using ambient air, water chillers, cold water, hypothermia…. 26 F water temperature would be necessary to achieve 16 PPM DO with no canna-plant roots or aerobic microbial colonies living in that water consuming DO.

I do not think mature canna-roots and beneficial microbes would thrive well in that freezing cold water even though that water would be highly supersaturated (>200% DO Saturation) with dissolved oxygen.

It is clear that intensive fish farmers can and do manipulate DO concentration in fish tanks water full of fish and how they do that is cost effective because this practice is common worldwide. If this oxygenation was not cost effective, why would they do that and they sell fish commercially, not commercial canna-buds.

Just thinking out loud… any thoughts?


Some very scientific responses here! I agree 8mg/L is a minimum I like to achieve with 10-11 be optimal which is hard to do using natural aeration. Spray bars, agitators, compressors using air stones are all garbage and pail in comparison to the use of straight oxygen with micro bubblers, liquid oxygen, or what I have adapted my farm to…degassing media in towers. With towers you can achieve 10-11mg/L output from “dead” water influent at 0-3mg/L. All other forms such as air stones will only get you to 7mg/L if your lucky and that is recirculated water not a straight through system like mine, I don’t recirculate only use fresh water. I would imagine a oxy generator or a compressed tank with minimal flow upwelling into a closed degassing tower on a recirculating system such as a hydro reservoir would easily bump oxy levels past optimal into 20-40mg/L even with a huge bio load and heavy salinity. Not completely sure but that’s why I’m on here to learn from others experiences. An interesting fact: if you plan to achieve 8+mg/L in your reservoir assuming using pure o2, don’t aerate using air and air stones in conjunction or you will actually decrease saturation as your bubbling your o2 right out of solution!
Any input on my max temp question? I.E. think I could utilize 90deg water if a 10mg/L oxy saturation level was maintained?


The purpose of supersaturation is to either reduce water consumption or to “bump up” high consumption systems. I run a flow through operation so no recirculation. I can run half the water flow at 20mg/L or a 1/4 at 40mg/L. Not exact figures but relative for an example. Water is expensive and less available so we are trying to use less. In high volume flow through I achieve 8-9mg/L in degassing towers and then “bump up” to 11-11mg/L with a milky white super saturated 80mg/L trickle from a pressurized line injected with liquid O2.


Hey Hash - I have noticed that many hydro canna farmers are totally convinced, actually believe that ambient air and elemental oxygen (O2) are the same gas… if you pump more air and bubble more air into the water, will that dissolve more O2 gas and nitrogen gas into the water if the barometric pressure remains constant?

I have also heard and read on forums that Hydro canna farmers do not test DO because DO meters cost too, DO testing is too much trouble and testing takes too much time and energy… elemental DO is a low priority matter. There is absolutely no need or reason for DO testing.

If you have an internet DO Chart, a thermometer and salinity meter, you can make a prediction (only a guess) as to what the actual DO Concentration and DO Saturation could be in nutrient water provided there are no aerobic roots or aerobic microbes in that water requiring and consuming DO continuously. Water temperature is commonly used to predict DO concentrations.

Nutrient reservoir water DO is tested with a thermometer and farmers constantly tither and always examine roots for symptoms of the dreaded “rotting root” symptoms.

When rotting root symptoms are abruptly discovered one morning out of the blue, then the race for the cure is on. An acute urgency to treat the rot and ensuing fungal infestations with home brewed microbial teas, H2O2, chemicals and fungicides. The treatment of the rot is usually preferred over prevention of the rot.

Spray bars, agitators, compressors and air stones are OK if simple mechanical aeration is the only goal (off-gassing dissolved CO2, elevating water pH and reducing ammonia, chlorine and other toxic gas concentrations. Oxygenating capabilities using ambient air in aquatic life support system is zip to marginal at very best.

Air is composed of 1/5 O2 and 4/5 Nitrogen gas. Air will usually work fine provided the aerobic biomass is minimal. When/if air is used primarily for oxygenation, the aerobic biomass must never exceed the continuous DO availability and minimal DO concentrations required by the collective aerobic biomass sustained by the life support system. If the aerobic biomass will not be healthy not thrive if the collective BOD is exceeded causing a low O2 environment.

But, if your aerobic bio mass is minimal, the small amount of O2 available in air (mechanical aeration) will work fine. When the BOD exceeds the O2 availability and BOD, the suffocation begin and it takes no mental giant to predict how that will end… which will not be good.

I have heard this great rule of thumb… for cultured aerobic plants, animals and microbes to be healthy and thrive within a controlled life support system, plenty O2 is far better that oxygen deficits (low to no oxygen) any day. NEVER exceed the collective biological oxygen demand required by all the aerobes sustained within your life support system.

How much O2 is plenty, what does plenty O2 mean? – DO must be tested for accuracy or you can certainly just hope and guess what your DO might be. For hydro canna, 16 PPM DO concentration is considered optimal or plenty so says some experts. But, actually testing the DO with a meter or DO test strips is necessary to confirm “plenty O2, low O2 or no O2.

Testing the water temp with a thermometer is cheap, quick and easy but that tells you nothing about real time DO concentrations. And no one actually test DO anyway for all kinds of reasons. As for fish farmers and fish hatcheries, routine life support system (fish tanks), DO testing with a DO meter is SOP, common, required and absolutely necessary.

Warm water fish live fine and thrive in 90F environmental water (lakes, bays, rivers, streams, estuaries and ponds) in the southern climes every summer, even at climes on and near the equator. 90F water may be problematic for cold water species. Low DO is the major problem that negatively affects all aerobic species, humans, fish, canna roots and microbes. Low oxygen advancing to hypoxia at the cellular level is the precursor to sickness, disease, death, and decay which always attracts fungal colonization (fungi wait patiently at the end of the life’s road for opportunities to feast so to speak). Fungi eat the dead and colonies thrive in decayed organic matter.

An exciting 1 minute experiment demonstrating the acute effects of insufficient elemental oxygen (O2). Try putting your head in a plastic bag, seal the bag around your neck. Water boarded has the same suffocating effect.

All of this O2 stuff is far more important to the pharmaceutical hydroponic canna grower because the Pro-growers always strive for optimal plant and beneficial microbial health which is vitally important for the end product, a drug that is certified and sellable with an MD’s written prescription.

Optimal health means quicker grow out time which means more product, which means more crops per year with higher yearly profits. The pro grower is interested in producing highest THC and CBC cannabinoid concentrations and medical purity requirements. Precision controlled life support systems can and do consistently produce healthy plants and the highest grade pharmaceutical products.

Whereas the hobby/recreational canna grower has totally different growing and end product goals and means to achieve these goals, production cost and equipment being a serious limitations for hobbyist. The hobby grower’s goals are to grow enough canna for him, his girlfriend/wife, other friends, Mom, brothers and sisters to be high every day, every year, year after year… to be suspended in a continuous steady state the “kumbaya moment” or bliss so to speak. Maybe like when the US Federal Government provided free whisky to Native American Tribes confined on Indian Reservations in Oklahoma during the 1800’s.

The product quality goal is hopefully the canna-buds will contain a sufficient concentration of THC to alter states of consciousness to get “high.” which is the only point of growing/consuming recreational cannabis.

Of course the hobby grower should never, ever sell the cannabis you grow without first buying a state license to produce and sell the drug.

Hobby/recreational canna production is so very different than professional production of pharmaceutical purity, quality and quantity when purity is regulated and controlled by state pharmacy laws and requirements. The US AG says growing/consuming cannabis violated Federal Laws and Federal Laws over-ride State laws with this MJ matter.

Experience for yourself the negative effects, the horror of suffocation caused by low elemental O2 insults. You will then understand how and why EC, PPM, pH and nutrition becomes totally meaningless compared to lack of oxygen and suffocation. Your 1st and primary concern will not be pH, EC or PPM, it will be O2, breathing and your immediate survival.

3 questions please:

  1. When you deliver 10-11 PPM DO, how many pounds of fish (biomass) are in your fish tank.
  2. A fish tank with the maximum biomass of fish in your tank, what is your DO Saturation @ 11 PPM DO?
  3. What is your fish tank water temperature @ 11 PPM DO?

Interesting stuff to talk about and think about for the scientific minded growers… totally meaningless and obnoxious for others to read or ever consider; just too far-out and strange to even think about… and that’s OK too.