Quantitative Airstone Test. an end to the hype

Mrfootball420 said:

without the so called hater you wouldnt have known that a 30g rez could reach max DO with a 10w pump and a 2in airstone.... your welcome!!!

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Good point, but I wasn't referring to you specifically, plenty of other guys hate on this dude

Excellent work and report, thank you!

Yo Heisenbuerg, you have any idea or data on what oxygen uptake rates are for mature plants? Also, will the plants actually absorb oxygen via contact with bubbles. Obviously DO levels are important but my thought is that perhaps the presence of bubbles actually matters.

The reason I say this is that A. there is no oxygen in solution in soil and B. people have experienced better results through placing more airstones in their containers. Or at least that is what they attributed the difference to.

Thanks,
LF

legallyflying said:

Yo Heisenbuerg, you have any idea or data on what oxygen uptake rates are for mature plants? Also, will the plants actually absorb oxygen via contact with bubbles. Obviously DO levels are important but my thought is that perhaps the presence of bubbles actually matters.

The reason I say this is that A. there is no oxygen in solution in soil and B. people have experienced better results through placing more airstones in their containers. Or at least that is what they attributed the difference to.

Thanks,
LF

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The real reason to pay attention to DO levels is to prevent pathogens from growing. Pathogens have a hard time living in any solution aerated to 6pp-8pp DO. Going above 8ppm is redundant in this context.

At 8ppm DO you are only supplying about 1% of what the roots require, the rest has to come from contact with air. The more oxygen available, the more oxidization can take place which allows more photosynthesis up top. That is why more bubbles equals better performance, and why aeroponic systems have wild growth. More oxygen = more feeding = more energy for photosynthesis = more growth. Studies have shown roots can spend only 1 sec of every minute in direct contact with (atomized) nute solution and plants still grow at amazing rates. When you consider this, the difference between 8ppm and 10ppm DO in the water seems negligible, and the importance of well placed stones becomes apparent.

http://en.wikipedia.org/wiki/Aeroponics
http://hydroponics-gardening-information.com/Oxygen.html

Well there you have it. I kind of suspected that it was not just do. I work as wetland biologist and even the most saturated soils will not support plants that do not possess adaptations to thrive in anerobic soil conditions.

What kind of pump stone set up are you using currently?

Hey legallyflying... great test and quite enjoying the ensuing discussion.

For shits and giggles, why not try one without an airstone? Just sink an open airline and see what that's all about. Just an idea, an maybe a valuable indicator that airstones actually do something!

Thanks again, great info +rep

legallyflying said:

What kind of pump stone set up are you using currently?

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I currently use a 35wt compressor to run 6-8 buckets, I use two 4inch blue stones in each bucket, and I leave at least an inch of air gap at the bottoms of the net cups so the roots can breath.

Interesting. One observation I made during the airstone test of the blue stones is that the 4" and the 6" seemed to disrupt the water equally or at least as close to equal as I can discern with the naked eye. Perhaps the 6" moved a little more water. However, while taking pictures of the stones with my underwater camera, the 6" seem to be putting off more actual "air stone" sized bubbles. It was almost as if the high pressure and smaller stone combo caused many more bigger bubbles to form. As if the pump was simply over sized for the smaller stone.

You make an excellent point however about DO rates and free oxygen amounts. It seems that for the ebb/flow crowd or those mixing large batches of soil water, a cheap pump and cheap stone is more than enough to reach full DO rates. There is absolutely no reason to be spending money on expensive diffusers or multiple stones in a rez.

For those that are growing with plants immersed in water, it is pretty obvious that free air levels are key as this is what plants need and any stone is going to easily surpass maximum DO pretty quickly.

To that end, I was thinking about the diffuser -vs- regular air stones. The diffuser puts out lots of bubbles, but becuase the pore size is so small, it clearly passes less air through it. So the discussion then turns to which approach lends itself to more oxygen/root interface time or...which approach achieves the most oxygen surface area-- smaller bubbles, but less of them or bigger bubbles. If you took the same quantity of air and made bubbles out of them then the smaller bubbles would have more surface area collectively. However, that is not the case in the diffuser-regular stone decision as the diffuser is clearly allowing much less air to pass through it based on naked eye observations.

I may be biased towards the regular stones because the diffusers are sooo expensive. But I feel that all things being equal, the 6" blue stone or 2" round is more applicable to DWC simply because of thee ease at which it allows air to pass through it. As for one or two stones per DWC bucket, I'm still on the fence. There is the advantage of having two stones in that if one becomes clogged you have a back up so to speak. The other side of the equation is that two stones, when reaching the end of a growth cycle and the buckets are absolutely full of roots, would more evenly distribute the bubbles through the root zone.

Any thoughts?

Heisenberg said:

At 8ppm DO you are only supplying about 1% of what the roots require, the rest has to come from contact with air. The more oxygen available, the more oxidization can take place which allows more photosynthesis up top.

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Do the air stones increase the density of O2 in the airspace inside the bucket? Would different stones supply more or less O2 to this space? Does the concentration or percentage of O2 in this airspace even matter?

Has anyone ever tried using pure o2 as a feed for the stones?

kannibis said:

Has anyone ever tried using pure o2 as a feed for the stones?

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That would be hella spendy.

Not really. An oxygen generator, such as the ones used for people with COPD. I would think it would supply more than the standard atmospheric amounts. But I'm curious if the effect would be worth the time and effort....

Late to the party but good read OP +rep

fuck. just typed huge repply and log in timed out. Have to do it later.

BendBrewer said:

I appreciate you demonstrating without a doubt that people buying those expensive stones are wasting their money.

I run a 1 stone per 3-4 gallons of solution. This test is perfect for me. Glad I didn't blow cash on the other stones.

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I agree,unless somebody is running a monster rez over 100 gallons this test is perfect,my rez's are 50 gal & the test backed up what i allreadt guessed.

I rarely leave rep but this is one instance.

Great job man,dont let the negative bullshit get ya down,most of the time all the negative nancy types are just trying to show their knowledge on the subject & whats the fastest way to show yer smart,dissagree with something then search for flaws.

Its marijuana growing guys not rocket sceince,everything is flawed but this is one kick ass bit of info.

Thanks man. Appreciate it allot. For everyone except those running dwc the test answers allot of questions. For dwc however, as heisenburgs contribution confirmed to me.. That while max DO rates are easy to achieve, DWC needs quite a bit more "free air" as the bubbles Interfacing with the roots provides them with oxygen. So in this respect the micro bubbles MAY be better but they certainly cause a large reduction on flow because of pore size.

They also clog rather quickly in organic or bene filled dwc. For this reason, the choice for me was push lots of air through cheap porous stones that resist clogging. At the end of each grow.. Throw them away and start fresh

Thanks man. Appreciate it allot. For everyone except those running dwc the test answers allot of questions. For dwc however, as heisenburgs contribution confirmed to me.. That while max DO rates are easy to achieve, DWC needs quite a bit more "free air" as the bubbles Interfacing with the roots provides them with oxygen. So in this respect the micro bubbles MAY be better but they certainly cause a large reduction on flow because of pore size.

They also clog rather quickly in organic or bene filled dwc. For this reason, the choice for me was push lots of air through cheap porous stones that resist clogging. At the end of each grow.. Throw them away and start fresh

hey legal thanks for your time in these DIY and test you have post I know people have disrespect sometime but theres alot of us that feel its all positive thanks legal

i use the four ft diffusers and every morning i wake up and there are NO bubbles. just standing water. so i lift them out of the water and clean em up and then i get little bubbles. i want lots of buubbles.

why not just turn on the air pump and stick the hoses right in the water? that looks like its giving great bubbles. also i dont wake up to clogged diffuser. what do i do?

Need more info. Pump type/output and is this in a Rez or dwc bucket?

I would buy a $1.25 6" blue airstone and be done with it. I'm currently using my 3' bubble line as a twistie tie on my mother plant. You probably could just use no stone but the blue stOne will increase DO rates and provide more mixing.