Recommendations please!!

Diy areocloner and diy cycle timer. each pin is 50 seconds. 2 pins on 4 pins off. Tap water only.
clones cut from undergrowth on a 4 week flowering plant. Was experimenting with cutting stems at an angle,str8 cut,spliting2stems and slicing the cambrium layer. 14 days from cut.

CoB_nUt said:

clones cut from undergrowth on a 4 week flowering plant. Was experimenting with cutting stems at an angle,str8 cut,spliting2stems and slicing the cambrium layer. 14 days from cut.

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Curious what the results of your tests were.
Could you give us those?

Keesje said:

Curious what the results of your tests were.
Could you give us those?

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Wasn't really a scientific type experiment, too many one off variables. I will check a bit later to see which ones have the most robust root system. I don't THINK it matters tho, all will root if given enough time. I know I know, not really helpful if you are counting on a certain amount of clones at a certin time. Out of 20-ish something clones, all have rooted well outside of two that are just starting to root.

I did some (non scientific) tests as well.
Also could not see much difference.
Only significant difference was that a higher temperature of the water made roots appear faster.

I've read quite often that the perfect water temp for hydro is actually 74 degrees, 75 degrees is a noticable drop in DO, but the argument is that it is also a perfect condition for bacterial growth.

shawnery said:

I've read quite often that the perfect water temp for hydro is actually 74 degrees, 75 degrees is a noticable drop in DO

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Well, you're wrong 2 times.
There is no 'perfect' water temperature for hydro.
There is more like a range of temperatures that are all good.
And some strains like colder water, some warmer water.
The temperature of your water is just 1 element of a whole range.

Diseases can appear at all temperatures. Some bacteria will grow well at 24 ° C / 75 ° F. Some at slightly higher temps, some at slightly lower.
But this is the matter for both beneficial bacteria as for bad bacteria.
Some other diseases like fungi will flourish at 15 ° C / 59 ° F, and others at 25 ° C / 77 ° F.
There is not 1 perfect temperature and also not 1 bad temperature.

About the oxygen.... Total and utter nonsense.
At 15 ° C / 59 ° F of clear sweet water contains 10.2 milli grams oxygen per liter
At 20 ° C / 68 °F water contains 9.2 milli grams
At 25 ° C / 77 ° F it is 8.4 mg's
At 30 ° C / 86 °F it is 7.6 mg's

So the difference between 74° F and 75 ° F will be approximately 0.2 milli grams.
That is not noticeable.
Besides that, this is the amount of oxygen the water will have when it is like a pool. Still standing water without plants.
Of course when roots would get in this water, they will consume oxygen, and you would think that they will 'eat' all the oxygen in minutes.
But with hydro you move the water surface one way or the other and the DO level will always be at it's maximum.
The moment you move the water surface just slightly the DO will rise to its max and there will be plenty of DO available.

But I have a question...
Why do you not look this up yourself on the internet?
Why be a parrot?
The cannabis world is a scene with lots of folklore. People just saying the most stupid things year after year, just because they heard or read it somewhere. Do your own research.

I do! I got that information from a scientific study!

I spend most of my time researching studies and journals from universities and scientists involved in hydroponic growing of many plants.

Perfection is something you try to obtain and you may be able to come as close as possible even if there is not an actual calculation that allows for perfection.

You made an assumption which is incorrect.

Then I apologize.

But show me the study where they say that at 75 F a noticeable drop in DO will happen.
Then I will write them an email that they are idiots.

Always make sure that it is from a legitimate source and that you really get to the source.
There are a lot of claims and reports that pretend to be academic but are not.

There is for example this (in my eyes) huge scam from this company that sells 02 emitters.
They also have some scientists mentioned on their website. From the University of Minnesota.
I can't understand why they want to appear on such a site with absurd claims.

Keesje said:

But show me the study where they say that at 75 F a noticeable drop in DO will happen.

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this chart is simplistic but i agree, not much difference.



the better question is root growth at 10.2 mg/L vs 8.6mg/L. only 1.6 difference but maybe if all other grow conditions are ideal or close to ideal, it does make a big difference?? that's the study i want to see.

Thats maximum DO holding capability not the DO level of the water in real life. If you had complete 100% aeration of a water source its complete DO would be at the level your text dictates, atleast this is my understanding frim research. As well from my understanding, though the numbers appear close they are not a true ratio of DO as the oxygen solubility drops.

I'll look around but I wouldn't post something and state it's validilty to prove a point, not my style. I do understand your lack of trust in cannabis here say though!

i'm not much into gadgets but a DO meter would be cool to have. especially if you really wanted to evaluate what your system puts out and compare to what the max value would be.

They are cost prohibitive but I have found ones for rent which I have been considering.

There is no need to have a DO meter.
You can be sure that if you move your water just a bit, that there will be the maximum amount of DO possible.

Let me explain a bit more also why it does not matter that there is a difference between 10.2 mg/L vs 8.6mg/L.
Compare it to a dog food bowl.
Let's say we have 2 bowls, A and B.
A contains 500 gramms and B contains 800 gramms.
Both bowls are connected to a large reservoir that will fill them up immediately when dogs eat from the bowl.
So if the dogs eat 100 gramms, the system fills it up a second later with 100 gramms of new food.
So no matter how much the dogs will eat from both bowls, the bowls will always be full.
And the dogs can eat as much as they want all the time.
It is the same with DO in water. No matter how much Oxygen the roots consume, in an instant the consumed Oxygen is filled up again.

Of course under extreme circumstances this will not happen.
Too much heat or water that does not move to much, things like that.
If water stands still in a system (for example in a rootball) some shortages can appear.
So just make sure your water surface moves a bit and your water circulates slightly, and all is good.

Keesje said:

Let me explain a bit more also why it does not matter that there is a difference between 10.2 mg/L vs 8.6mg/L.

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i disagree. the only way to really test would be to have 2 clones in identical grow enviros with the only difference being the DO in each.

a plant exposed to 10.2 "could" grow better/faster/etc. vs 8.6 if those levels were maintained for the entire 12 weeks (3 wk veg/9 wk bloom).

rkymtnman said:

i disagree. the only way to really test would be to have 2 clones in identical grow enviros with the only difference being the DO in each.

a plant exposed to 10.2 "could" grow better/faster/etc. vs 8.6 if those levels were maintained for the entire 12 weeks (3 wk veg/9 wk bloom).

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Sorry to say, but you are wrong.
Of course you can disagree with me, and I have no problem with it.

But I guess you did not read or not not understand my explanation with the dog bowls.
Which hurts, because I did my best.

Let me give it another try.
Roots of most plants use 200 mg of oxygen per kilo of roots per hour.
They keep on consuming it.
Example: there is 10 mg in a liter at a certain temperature, and the plant has 1 kilo of roots and your DWC reservoir is 20 liter...
That means 200 mg of DO in the reservoir.
Then there would be enough oxygen for 1 hour.
In itself it is true, but something else will happen.
After 6 minutes (1/10th of an hour) the roots would have theoretically absorbed 1/10 of the oxygen they need.
So instead of 200 mg in 20 liters, there now is 180 mg in 20 liters.
But it is not true. Because of the movement of the water surface, the absorbed 20 mg will be replaced immediately by fresh oxygen.
So again there will be the maximum of 200 mg in the 20 liter.
The roots can absorb how much they want, there will always be the maximum DO in the water.

When the temperature is a bit higher, the maximum amount of DO in a 20 liter reservoir will be a bit lower.
But still there is plenty of DO.
For example: there is now 8 mg in a liter at a certain higher temperature, and the plant has 1 kilo of roots and your DWC reservoir is 20 liter...
That means 160 mg of DO in the reservoir.
It looks like there is not enough oxygen for 1 kilo of roots. You are missing 40 mg.
After 6 minutes (1/10th of an hour) the roots would have theoretically absorbed 1/10 of the oxygen they need (20 mg per 6 minutes)
So instead of 160 mg in 20 liters, there now is 140 mg in 20 liters.
It looks like it is not enough for the remaining 54 minutes.
But because the absorbed oxygen is replaced right away, the amount of DO is again 160 mg in the reservoir.
And after another 6 minutes (12 minutes total) the roots have absorbed another 20 mg, and the DO in the reservoir will be again 160 mg.
And after another 6 minutes (18 minutes total) the roots have absorbed another 20 mg, and the DO in the reservoir will be again 160 mg. Etc.
After 60 minutes the roots will have gotten all of their 200 mg of DO needed and the level of the DO is still 160.

Even if the roots would like to have more DO... let's say 500 mg per hour per kilo of roots. There still will be enough oxygen all the time. Just for the simple fact that everything the roots absorb is immediately replaced by fresh oxygen. It has to do with air pressure, that will 'push' oxygen into the water continuously.

So it does not matter if there is 10 mg or 8 mg of DO per liter > There is always more oxygen then the plant can absorb.
Only when the maximum amount of DO a liter water can hold becomes very low (at 40 ° C or something like that) then you get in trouble.
The roots then absorb much faster then fresh oxygen can get dissolved in the water.

Also when your reservoir is too small for the amount of kilo's of roots you can get into trouble.
But I guess in that situation it does not really matter if your water holds 8 mg or 10 mg of DO per liter.
Maybe your plant will die an hour later.

If you still disagree with me, I invite you to explain to me where I am wrong.
Maybe I missed something.

Keesje said:

But I guess you did not read or not not understand my explanation with the dog bowls.

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i did read it. i'm saying that the dog bowls are not connected.

if dog 1 can eat 500g a day and lose weight but dog 1 if given 800g a day would maintain weight, than 500g is not enough food for dog 1.

same thing with clone A, if given 8.6 DO and it grows at x rate. if clone B, if given 10.2 DO would grow at x rate then the DO would not matter since they both are growing at x rate.

but if clone B grew at x+y rate because of more DO, the the level of DO for clone A is not enough and the plant could use more DO.

either way, post a scientific study and i'll be glad to read it. i don't think there is one for cannabis. a study about lettuce is meaningless.

There is ALWAYS a reason to check and double check you assumptions! I know I always check and recheck over and over and still find faults in my reasoning.

Whether you are right or wrong in this instance is neither here nor there because we are speaking at the moment of ensuring our understanding of a set of facts which are in dispute.

We all know that there is more folklore then facts out there so why would any of us take our words for it? Shit! I told you I read a university study and still you find doubt in my words and rigjtfully so!

When it comes to understanding hydro, ferts and DO interact and they do is very important no matter the crop.

shawnery said:

When it comes to understanding hydro, ferts and DO interact and they do is very important no matter the crop.

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my point is each crop has it's own set of requirements : a fert level for tomatoes might be too much for greens. a DO level for flowers might me too little for cucumbers.

that's why i said a cannabis specific study would be interesting. if there is one.

something like this but for DO levels, not root zone temps, but specifically for cannabis:


Cornell University researchers have conducted studies (http://www.cornellcea.com/attachments/Cornell CEA Lettuce Handbook .pdf) to identify the specific temperatures that are ideal for hydroponically-grown vegetables.

“Cornell researchers found the temperature of the nutrient solution had a greater effect than the air temperature,” Raudales said. “Lettuce plants exposed to air temperatures ranging between17ºC (62.6ºF) and 31ºC (87.8ºF) had consistent yields as long as the nutrient solution had a consistent temperature of 24ºC (75.2ºF). This research was done in the 1990s, but it still has application today.

“Cornell researchers did a similar study with spinach and they found the optimum root temperature was 22ºC (72ºF). They tested air temperatures ranging from 16ºC to 33ºC (60.8ºF-91.4ºF) and they found as long as the root temperature was 22ºC, the air temperature could be in that range and plants still produced optimum yields. For tomatoes the optimum root temperature is 25ºC (77ºF).”