Advanced aeroponics - or how to get fuzzy roots and be a happy grower

Why aeroponics? Most people would agree that aero is the apex of hydroponics. Ok, maybe its more like some people would agree It is supposed to give you faster growth, faster harvests, bigger buds, higher yields, etc etc etc.

Ok, fine. All of that is true – in theory. In my experience, YMMV

Yes, I have seen significant increases in yield...and total disasters. Sometimes things move along at a break neck pace, and then you screw up and things slow down or stop.

In other words, aero can help a good grower, but it wont fix the problems of a bad grower. The environment – things like lighting, temps, humidity, PH control, nute balance, etc etc etc all seem to have a much larger impact on yield and plant health than simply switching from regular hydro modes to aero.

I measure my success or failure by grams per day – NOT gm/watt. Grams/watt is a useless, stoner science metric, but lets not get into that mess
I track how many dry grams I end up getting for each day I spend growing. More grams per day is good, less is bad.

When I was growing in soil I averaged in the 4 to 5 grams/day range. When I switched over to hydro, I went up to 5 to 6 gm/day. When I tried HPA I got up to the low 7’s. With AA I have hit very close to 8 gm/day. Well, not counting those grows where things did NOT go so well

Now all of those grows were in the same 4 ft tall, 7.3 sq ft tent with the same 320 watt LED lights, same ventilation, etc etc. I'm sure some of that improvement over time is due to me just getting better at this game in general.

In any case, aero isn't the be all, end all, fix all growing method, but it can be better if you can make it work correctly.

All of that said – I don’t give a crap about higher yields, or faster grows. Even with a bad harvest, I end up with plenty of meds for my use. I got into hydro and then aero because growing is just boring as shit! Plus I am a gizmo and gadget kind of guy and the hardware was interesting and something to play with.

But – then I discovered fuzzy roots, and I was hooked. Addicted is probably not too strong a word. I don’t really care what the plants look like or how much I yield. If I have fuzzy roots I am a happy man.

But #2 – are fuzzy roots really the ultimate form of roots? Based on the little actual scientific research I have seen, Id say yes. Those tiny hairs are supposed to increase nutrient up-take efficiency, and speed up the entire process.

I have no idea what kind of % increase in any aspect of growth fuzzy roots have over smooth roots. I'm sure it is a positive factor, but who knows if its 5% or 30% or? I've seen plenty of fantastic looking LPA, HPA, DWC,, ebb/flow, or NFT grows even though they had smooth roots.

So fuzzy hairs are not really necessary to have a great grow – no matter what kind of hydro you are running. Aero isn't necessary either.

My advice is don’t bother to get into aero just in the hope you will have automatically increased yields and huge buds. You might, or you might not see any significant improvements over your current growing style.

On the other hand, if I havent scared yo u off already, it can be a lot of fun if you are into learning new stuff, being on the cutting edge, experimenting, playing with gizmos, gadgets, etc. And who knows, you may even see some improvements in your grows!

Aero can be done very simply and cheaply with something like LPA. Done correctly (most people way over water) you should see a slight improvement over deep water techniques. You can move up to HPA, and keep it simple, but if you don’t really have the correct setup, proper timing schedule, equipment, etc, you will end up with smooth roots and see little to no improvement over LPA. The same is true of AA. If not done correctly, you will again end up with smooth roots.

If you are going to end up with smooth roots, Id recommend you stick with LPA. Its a LOT less trouble and a LOT less expensive and more reliable, easier to set up, dial in etc etc.

But – if you want to run at the peak and have fuzzy roots, then the only way I know is to spend the money and set up the system correctly and then spend the time dialing it in.

Fuzzy roots are not easy. They are much easier to loose than to get. They are fragile and sensitive to several factors. It will take time to dial in your system. You will need to experiment and you may need to kill off some (lots actually) seedlings along the way. In my case, its been a bunch of seedlings. I could be called a mass murderer of seedlings. Just this year, I probably started and killed off at least 2 dozen babies working out some changes to the system last spring and into the summer. All of that takes time too, so if you are in a must succeed situation where you cannot afford to have a bad or delayed harvest, then its probably not wise to switch over to aero just yet. Get some meds stored up just in case first.

I’ll go into the details of my personal setup in the next few posts, but feel free to jump in with questions, comments, etc.

Oh – I should warn you all that I am on a very limited budget, so pretty much everything I have done is as cheaply as possible. I'm also not a super neat builder. I'm into cheap, fast, functional, and cheap. So don’t expect to see ‘clean room’ grade building details I’m talking about you @SuperiorBuds and any one else who builds like they work at NASA!!

That said, don’t throw any stones unless you can meet or beet roots like these. Remember – its ALL about the fuzzy hairs as far as I'm concerned. Every thing else is secondary.



I forgot to tag some folks... @rkymtnman @SuperiorBuds @Yawningtears @Wastei @firsttimeARE I know there are other aero guys I have forgotten, so feel free ot tag anyone you think might be interested.

I'm just interested about specs for a comparison. Do you have any pics and specs of the setup? What controller/timer do you use?

I'm wondering about Spray nozzle sizes, spray time intervals, pressure and accumulator tank size and positioning. Do you just pressurize the nutrient solution with the compressor or can you actually change the air to water mix ratio?

Here's my system up and running. Regular HPA. Draws under 20w with 7.5h of power redundancy.

Changed the nozzles this run to stainless steel ones. Seems to be working even better than on the last run. Easier to switch out and
gives me more space for the roots to grow, had a little problem of the roots growing into and covering the nozzles last run.

For me the root "fuzz" is not as important as having many well developed laterals.

Wastei said:

I'm just interested about specs for a comparison. Do you have any pics and specs of the setup? What controller/timer do you use?

Click to expand...

My HPA setup was quite different from yours - but remember I was and am still after fuzzy hairs. I was wanting to go into the theory before I got into hardware, but I will give you a quick rundown. Much of the hardware and setup is the same with the AA setup.

My timers are cheap digitals with solid state relays (about $8 ea) that can do 0.1 sec intervals. Im currently using three - one for each nozzle and one for an alarm so I dont forget to turn the dam nozzles back ON after working on the system. On the HPA system I used a single timer for three nozzles. Nozzles were stainless .06mm orifice, with ADV's. One solenoid per nozzle placed as close to the nozzle as possible to reduce runon spray.

Accumulator tank was 5 gal plumbing type pressure tank running at 130 PSI, and feeding into a pressure reducer set to 90-100 PSI. Pump was a cheap espresso machine pump. Rex my same 10 gallon icechest. I run drain to waste.

My root chamber is a 55 gallon fabric chamber made from two 30 gallon fabric growing pots stitched together. its 24" in diameter x about 29" tall. I used three of those SS nozzles in the chamber. Timing was around 0.7 seconds ON x 70-90 seconds OFF. At that pressure those nozzles were about 0.7 gph each IIRC.

I pretty much filled that 55 gallon chamber with my last HPA grow. It was a single C99 plant. Yielded well over 4000 grams wet. I forget the exact dry weight, but it was close to 1 KG. The main down side to that grow was it took about 140 days from seed to harvest and ended up at 7.4 gms/day IIRC.

The biggest differences from my point of view are the size of the root chamber, and the flow rates. My chamber is much larger than yours and my flow rates are much lower. The hardware isnt that important.
Here are a couple of pics.

This is about mid way through the grow looking down through an access hatch.


This is near harvest.


I had to have some surgery and ended up harvesting them at least a week early, maybe two.

Wastei said:

gives me more space for the roots to grow, had a little problem of the roots growing into and covering the nozzles last run.
For me the root "fuzz" is not as important as having many well developed laterals.

Click to expand...

Yup - the roots will always go for the nozzles. They know where the water source is - always!

There is nothing wrong with not worrying about fuzzy roots. I checked your grow and you plants look great. Plus, it sure makes things easier

Larry3215 said:

My HPA setup was quite different from yours - but remember I was and am still after fuzzy hairs. I was wanting to go into the theory before I got into hardware, but I will give you a quick rundown. Much of the hardware and setup is the same with the AA setup.

My timers are cheap digitals with solid state relays (about $8 ea) that can do 0.1 sec intervals. Im currently using three - one for each nozzle and one for an alarm so I dont forget to turn the dam nozzles back ON after working on the system. On the HPA system I used a single timer for three nozzles. Nozzles were stainless .06mm orifice, with ADV's. One solenoid per nozzle placed as close to the nozzle as possible to reduce runon spray.

Accumulator tank was 5 gal plumbing type pressure tank running at 130 PSI, and feeding into a pressure reducer set to 90-100 PSI. Pump was a cheap espresso machine pump. Rex my same 10 gallon icechest. I run drain to waste.

My root chamber is a 55 gallon fabric chamber made from two 30 gallon fabric growing pots stitched together. its 24" in diameter x about 29" tall. I used three of those SS nozzles in the chamber. Timing was around 0.7 seconds ON x 70-90 seconds OFF. At that pressure those nozzles were about 0.7 gph each IIRC.

I pretty much filled that 55 gallon chamber with my last HPA grow. It was a single C99 plant. Yielded well over 4000 grams wet. I forget the exact dry weight, but it was close to 1 KG. The main down side to that grow was it took about 140 days from seed to harvest and ended up at 7.4 gms/day IIRC.

The biggest differences from my point of view are the size of the root chamber, and the flow rates. My chamber is much larger than yours and my flow rates are much lower. The hardware isnt that important.
Here are a couple of pics.

This is about mid way through the grow looking down through an access hatch.
View attachment 4761905

This is near harvest.
View attachment 4761906View attachment 4761907

I had to have some surgery and ended up harvesting them at least a week early, maybe two.



Yup - the roots will always go for the nozzles. They know where the water source is - always!

There is nothing wrong with not worrying about fuzzy roots. I checked your grow and you plants look great. Plus, it sure makes things easier

Click to expand...

Awesome! Thanks for posting this, much appreciated. I'm still dialing in the system with the new nozzles. In the future I'm planning on adding a humidity and temp sensors in one of the root chamber which in turn regulates spray time. Acting as a control bucket.

I would like it to have a range of 1.5-3 seconds spray time depending on humidity/temps in the rootzone. Changing as the season go.

Really need a PC to test some code.

I doubt a humidity sensor will work. The humidity in a sealed root chamber like yours will always be very very close to 100%. With all those micro droplets evaporating all the time it cant be any other way. It will drop when your recirculating pump kicks on and brings in fresh air, but quickly go back up.

The temp sensor might be a good idea in your case because you are using the spray to cool the roots. You're not interested in fuzzy hairs, but you still do need to control temps. If you were setting the timing low enough to get fuzzy hairs, you would have very little cooling effect.

For example, in my 55 gallon chamber, my flow rate right now is about 2.5ml per ON cycle and about 0.75 gallons per day. Im guessing you have at least 10 times that flow rate per cycle in a chamber 1/10th the size. That means you are getting about 100 times the cooling than I would get in a similar situation.

My chamber stays cool because of evaporation on the outside surface of the fabric. Much like a swamp cooler. My chamber stays 7 to 10 deg F cooler than room temp - BUT - my root chamber is not in the grow space inside the tent. Thats a very important difference. Its why I have to heat the chamber most of the time or it stays too cool.

Larry3215 said:

I doubt a humidity sensor will work. The humidity in the root chamber will always be very very close to 100%. With all those micro droplets evaporating all the time it cant be any other way. It will drop when your recirculating pump kicks on and brings in fresh air, but quickly go back up.

The temp sensor might be a good idea in your case because you are using the spray to cool the roots. You're not interested in fuzzy hairs, but you still do need to control temps. If you were setting the timing low enough to get fuzzy hairs, you would have very little cooling effect.

For example, in my 55 gallon chamber, my flow rate right now is about 2.5ml per ON cycle and about 0.75 gallons per day. Im guessing you have at least 10 times that flow rate per cycle in a chamber 1/10th the size. That means you are getting about 100 times the cooling than I would get in a similar situation.

My chamber stays cool because of evaporation on the surface of the fabric. Much like a swamp cooler. My chamber stays 7 to 10 deg F cooler than room temp - BUT - my root chamber is not in the grow space inside the tent. Thats a very important difference. Its why I have to heat the chamber most of the time or it stays too cool.

Click to expand...

Yes temp sensor is probably the best way to go. I designed the system to be very modular and had root chamber temps and cooling as main priority.

I'm going to the location today I think. Maybe I'll post some pictures on the clone root fuzz, lol. Thanks again for starting a thread @Larry3215. I think its very much needed for people starting out with Aero.

I wish I was living in the states and had access to all the hardware stores you guys have. You don't know how lucky you really are to just be able to buy PVC pipes, glues, pumps, nozzles etc in a actual hardware store. I have to order exactly everything, wait weeks and then test things out.

very cool setups for both of you guys!!!

and i agree with you @Larry3215 , those fuzzy roots are just sexy as hell.

keep up the pics!!

I was at location today. Added some shock to the reservoirs and checked root development in the system. Forgot to put the filter bags in, not installed on the picture:
Something fuzzy going on! Lol Cheers!

Larry3215 said:

My HPA setup was quite different from yours - but remember I was and am still after fuzzy hairs. I was wanting to go into the theory before I got into hardware, but I will give you a quick rundown. Much of the hardware and setup is the same with the AA setup.

My timers are cheap digitals with solid state relays (about $8 ea) that can do 0.1 sec intervals. Im currently using three - one for each nozzle and one for an alarm so I dont forget to turn the dam nozzles back ON after working on the system. On the HPA system I used a single timer for three nozzles. Nozzles were stainless .06mm orifice, with ADV's. One solenoid per nozzle placed as close to the nozzle as possible to reduce runon spray.

Accumulator tank was 5 gal plumbing type pressure tank running at 130 PSI, and feeding into a pressure reducer set to 90-100 PSI. Pump was a cheap espresso machine pump. Rex my same 10 gallon icechest. I run drain to waste.

My root chamber is a 55 gallon fabric chamber made from two 30 gallon fabric growing pots stitched together. its 24" in diameter x about 29" tall. I used three of those SS nozzles in the chamber. Timing was around 0.7 seconds ON x 70-90 seconds OFF. At that pressure those nozzles were about 0.7 gph each IIRC.

I pretty much filled that 55 gallon chamber with my last HPA grow. It was a single C99 plant. Yielded well over 4000 grams wet. I forget the exact dry weight, but it was close to 1 KG. The main down side to that grow was it took about 140 days from seed to harvest and ended up at 7.4 gms/day IIRC.

The biggest differences from my point of view are the size of the root chamber, and the flow rates. My chamber is much larger than yours and my flow rates are much lower. The hardware isnt that important.
Here are a couple of pics.

This is about mid way through the grow looking down through an access hatch.
View attachment 4761905

This is near harvest.
View attachment 4761906View attachment 4761907

I had to have some surgery and ended up harvesting them at least a week early, maybe two.



Yup - the roots will always go for the nozzles. They know where the water source is - always!

There is nothing wrong with not worrying about fuzzy roots. I checked your grow and you plants look great. Plus, it sure makes things easier

Click to expand...

That root picture looks like the lorax moustache. Epic roots.

Seems complicated. Also dangerous. 100PSI?! Shit could puncture you

for us noobs to aero, what is the difference b/t AA and HPA?

and for both you aero growers, i assume that nute use is extremely reduced when going aero?

and compared to rdwc/dwc, how quickly can shit hit the fan? minutes, hours, days? i would guess you guys have some type of battery backup for the essential components?

rkymtnman said:

for us noobs to aero, what is the difference b/t AA and HPA?

and for both you aero growers, i assume that nute use is extremely reduced when going aero?

and compared to rdwc/dwc, how quickly can shit hit the fan? minutes, hours, days? i would guess you guys have some type of battery backup for the essential components?

Click to expand...

From my understanding the main difference is how the system is pressurized. A diaphragm pump that build pressure makes some noise. Not much when it's pressurized, but a lot when you prime the system. Removing all the air. That's for HPA

AA gets pressurized by a compressor instead which in turn can hold pressure for longer time periods and will last longer before breaking.

I have emergency power for 7.5 hours for the main system if we ever encounter such long power loss where I'm from. It also has an alarm system. Planning on installing some sort of messaging system alarming me when the system turns to ups/emergency power.

That's one for the future. 7.5h is enough for very long power outages at least.

I haven't tinkered that much with lowering nutrient strength. I will never go above 1.1 EC this round, I believe at least. I will try to lower it as much as possible.

I'm gonna aim for 0.8 EC throughout flowering and see how the plants reacts. What they want is what they're getting..

Wastei said:

I have emergency power for 7.5 hours for the main system if we ever encounter such long power loss where I'm from. It also has an alarm system. Planning on installing some sort of messaging system alarming me when the system turns to ups/emergency power.

That's one for the future. 7.5h is enough for very long power outages at least.

I haven't tinkered that much with lowering nutrient strength. I will never go above 1.1 EC this round, I believe at least. I will try to lower it as much as possible.

I'm gonna aim for 0.8 EC throughout flowering and see how the plants reacts. What they want is what they're getting..

Click to expand...

so what is the main thing you guys gotta watch out for? roots drying out??

rkymtnman said:

so what is the main thing you guys gotta watch out for? roots drying out??

Click to expand...

Very true. Main thing is nozzles being restricted and/or stop working. With my new ones I can change them out pretty easily. You usually change nozzles and clean the ones the run before in vinegar solution between runs. Switching to fresh ones, or refurbished.

@Larry3215 glad to see you back dude!

@rkymtnman differences between hpa and aa are huge and many. Nozzles are different - aa stands for air atomizing. These are usually internal mix nozzles that mix air coming from compressor and nutes solution. We tend to use nozzles that requires only air pressure, usually pretty low 5-15psi, while water is in most cases gravity or syphon fed.
HPA on the other hand mainly requires high pressure nutes solution from either accumulator tank or directly from the pump - 60-90psi. It does not have the compressor/air tank in the picture.
In addition nozzle prices are quite different. Good SS aa nozzle can go up to $250 and picking up the right one for the chaimber and application is quite tricky and gets costly - not trying to push you away from "the way" - just stating the facts.

As for nutes solution its usually 1/3, even less from the normal ppm.

I'm sure Larry will chime in with more details

Wastei said:

Something fuzzy going on! Lol Cheers!

Click to expand...

See - I was right! Fuzzy hairs make you a happy grower

firsttimeARE said:

Seems complicated. Also dangerous. 100PSI?! Shit could puncture you

Click to expand...

HPA and AA are both more complicated than other types of hydro, and yes, HPA can be dangerous if you dont take care. Exploding 5 gallon steel tanks filled with water or air under pressure can ruin your day for sure!

AA is not quite as dangerous because the tanks dont have water in them, so less mass to cause damage and less likely the tank will fly through a wall. But normal safety precautions are fine - about what you would use for a contractors air compressor, which most folks never think of as dangerous.

As far as the complexity, once you get the hang of it, its no big deal. Also, once your system is dialed in, there is very little work to do other than check the roots periodically, and do rez changes, check PH and the normal grow stuff. Other than minor tweaks to the timing, all Ive been doing is normal rez stuff and growing chores since these babies got started.

Of course, "getting the hang of it" can take a little while

rkymtnman said:

for us noobs to aero, what is the difference b/t AA and HPA?

Click to expand...

The key difference is in how the nutes get atomized.

In HPA hi pressure is used to atomize the water as it leaves the nozzle. It can be anywhere from around 40PSI up to 130 PSI depending on the nozzles, type and size of chamber and what droplet size range you want. Once you have your nozzles chosen, your only variable is the water pressure you feed to the nozzles. Higher pressure = smaller droplets. Lower = larger droplets. The water is pressurized with a hi pressure pump, and stored in an accumulator tank (the bomb), then fed to the nozzles by a solenoid. The solenoid is used to control the ON/OFF timing.

With AA, you are using air pressure to atomize the water. Think air driven paint spray gun, air brush, etc. In AA the air pressure and water pressure are both very low. In my setup, with the nozzles Im using now, the air pressure is only 10 PSI, and there is no water pressure at all. The nozzles I'm using suck the water up out of a small tank - sitting by the root chamber - by siphon action. The air compressor Im using is still running at its normal max of around 90 PSI, but Im not worried about that.

The main advantage to AA over HPA is the added degree of control you have over the droplet sizes, and the flow rate. This does add extra complexity because you have more things to adjust, but is really no big deal. The advantage is that you can create a much better, or more finely tuned mist environment. AA nozzles also are much harder to clog. The orifices and passages are much larger than HPA nozzles. A typical AA system is also a bit less complex with a lower parts count than a similar quality HPA system. The difference isnt big though.

The main downside to AA is it does cost more to get started. Thats mainly due to the nozzles. AA nozzles start around $25 ea and go up to $200 or more. HPA nozzles start at $5 ea and rarely are more than $10. With AA you will save some money from the lower parts count, but then the nozzles bite you in the butt. Using nozzles like mine, you could build an AA system for maybe $50 more than a similar HPA system, so not that much more.

rkymtnman said:

and for both you aero growers, i assume that nute use is extremely reduced when going aero?

Click to expand...

Maybe. It will depend on your timing, flow rates, chamber size, and also if you have fuzzy roots or not. I will go into that more when I get to the theory, but basically is has to do with droplet evaporation, plus the increased nute up-take efficiency of fuzzy hairs.

For example, right now my autos range in age from about 3 weeks to about 6 weeks. Im still running at 0.4 EC, and my water is 0.2 to start. So Im only runing 100 PPM worth of nutes on the 500 scale. I might have to go up to 0.6 EC later in flower, but I doubt I will need to go above that. I have not been above 0.8 in a long time.

Note that the babies do not look hungry. They all look about that color.

rkymtnman said:

and compared to rdwc/dwc, how quickly can shit hit the fan? minutes, hours, days? i would guess you guys have some type of battery backup for the essential components?

Click to expand...

Im my system the roots can go without being sprayed for maybe 4 hours before serious root damage starts. I know that from repeated, unintentional "experiments" on my part. My plants have survived periods of stupidity as long as 12 hours, but showed leaf issues from significant root die back. Every single time this has happened to me has been due to shear dumbassery or growing while stoned. I finally rigged up an alarm

I do not have a UPS setup. I've had a few power outages, but I was home and handled short ones by spraying the roots with a spritz bottle every 15 minutes or so. On the one long outage last winter, I hooked my generator and ran the system that way for several hours.

In a setup like @Wastei has, he could probably go much longer because he has standing water in the bottom, and a sealed bucket. My fabric chamber allows much faster drying out.

Wastei said:

What they want is what they're getting..

Click to expand...

Thats my philosophy too. I dont believe in sticking to some number just because. Let the plants tell you if they need more or less. They almost never lie

VandalBee said:

I'm sure Larry will chime in with more details

Click to expand...

Hey, good to see you! Yup, you nailed it. As usual, my answers are a bit long winded compared to yours

Be sure to jump in with details of your setup and a progress report!

At some point I want to do a post covering some basic theory, and some of the flow rate, and timing math involved. Dont anyone freak out. It can all be handled in a simple spread sheet Then I'll get into more details on my exact setup incase anyone want to try to duplicate it.

I actually think I found some atomizer heads laying around. Remember ordering them when I was starting to gather parts for Aero, a lot of trial and error. Never even tried them. I know they are Chinese copy's of very expensive ones.

Maybe I'll play around a little with AA on the side. Got both nozzles and solenoid valves for AA. These are AA nozzles right @Larry3215? Remember they being expensive. Think I have 8 sets of these:

Cheers!

I cant be 100% sure, but those look like HPA nozzles. I think they are what are called impact nozzles - like these:



You need to check the specs carefully as many of those have very hi minimum operating pressures. That one I linked to has a minimum of 400 PSI. The trick is - can you trust the specs with clones? I have seen several clones with insanely inaccurate specs or with good specs, but not actually built to those specs.

I tried some plastic versions of that type of nozzle that worked down to 40 PSI - sort of. The droplets were way too big on average (making for crappy hang times), and the flow rate was through the roof.


AA nozzles will have two connections. One for water and one for air. If there is no air connection or port on the nozzles itself, then they are hydrolic nozzles and will only work for HPA type setups.

Also, one thing to check when picking out solenoids is the working pressure range. The one in that pic has a working pressure range from 1.5-8 kg/cm^3. Thats about 21 PSI to 117 PSI. Note the low number is the minimum pressure for it to work. That one will be fine for HPA because you will probably never go under 21 psi ever, but it will be very iffy for AA aero. For example, I need solenoids that have much lower working pressure range because the air pressure runs from about 5psi to about 30 max with my current nozzles. Im running 10 PSI now. I have other nozzles that run from 10-60 psi air and zero to 40 psi water. So its important to pick your solenoids to match the pressure ranges you think you may be running at.

Another tip I have learned the hard way when working with inexpensive solenoids - stay well under the max pressure. They have a bad habit of failing when you get too close. I would stay at 100psi max or under with those.

Ok, lets talk some theory and how to translate that into hardware choices. This applies to HPA and AA.

First I have to give most of the credit for this theory to a user named Atomizer. I don’t like him very much for reasons I wont go into here, but he really know his stuff as far as the science behind HPA and AA aero. He and I have tangled a few times and he accused me – falsely – of not giving him credit for his ideas. So I now go out of my way to be sure to LOUDLY give him his due. He seems to crave the attention. There were a few others, like Fatman, and others I have forgotten, but Atomizer was the man to listen too. He is a total jerk, but a really smart jerk.

Fuzzy roots are fragile and finicky compared to smooth roots. Those little hairs are easy to kill off and kind of picky as far as environment. Any root bacteria will kill fuzzy hairs long before it kills the base root or the plant. Too much chlorine, or H202, etc will also kill them off. Even too much water will prevent their growth.

What they like is an environment filled with very small drops of water with just enough nutes. According to Atomizer, the ideal droplet size range is from about 20 microns to about 80 microns with a median of around 50 microns. I think it works better if the median is lower with a size range from about 10 microns to 80 microns with a median closer to 40.

However, its hard to find good droplet size info for most nozzles that will work in small root chambers like mine – which is about 55 gallons. Spraying Systems has some charts available for some of their nozzles, but not all. Even then, those charts don’t cover all the options as far as different air and water pressures or siphon heights, so you are left guessing most of the time.

Fortunately, there is a simper test you can do that will get you in the ball park – measure the “hang time” of the mist in the chamber. You can also just look at the mist by eye and judge it after you get some experience.


I can go into that more if anyone has any questions. I also have several videos I can post.

To produce that ideal mist environment, you need nozzles that make droplets in the right size range – but – you also need to consider the flow rate. Remember, you don’t want the roots tooooo wet or toooo dry. You also want all the roots to get more or less the same amount of mist, so you need to think about coverage. You need enough nozzles placed around the chamber so that all sides of all the roots of each plant get covered, while none of them get too much.

To begin with, you need an ON time that will “fill the chamber” with just the right number of droplets, but not too many. You calculate that ON time based on the flow rate of the nozzle at the pressure you need that makes the right size droplets. Remember, higher pressures make for smaller droplets – but – those higher pressures also make for higher flow rates.

Atomizer recommends that a chamber needs between 0.02 to 0.06 ml of water per gallon of chamber volume for each ON cycle to fill the chamber. The amount is lower during early growth and higher later on.

My chamber is 55 gallons, so in the early growth stage I need a total of 55 x 0.02ml = 1.1 ml per ON cycle. That number will of course change with different chamber sizes. Because I am running two nozzles, that means each nozzle needs to put out 0.55 ml during each ON cycle.

My nozzles have a flow rate of 4 LPH, or about 1.1 ml/second. So to get .55 ml into the chamber takes 0.5 seconds of ON time for one nozzle. That means your minimum ON time will be 0.5 seconds when running two nozzles in a 55 gallon chamber.

Max On time will be 3 times longer (0.02 to 0.06 is three times), so that equals 1.5 seconds ON time.

So now you have a range of On times for a nozzles with a flow rate of 4 LPH going into a chamber of 55 gallons.

The OFF times are chosen based on your hang time. You never even want the chamber to be without mist. You want your next ON cycle to start BEFORE all the mist is gone. Actually, before it start to fade much at all. Remember, we are after a uniform environment - NOT a wet/dry cycle.

The perfect environment for fuzzy roots is one that never changes. It never gets too wet or too dry and always stays exactly in the middle of that perfect Goldilocks zone. Unfortunately, that's not possible with any tech that's affordable as far as I know. So we are left to make our best guess and try to get as close as possible. We do that based on hang times and by never letting the mist get too dense or too thin.

To test, I run the nozzles at a given On time for a few minutes to let the chamber get stabilized and totally full of mist. Then I shut off the nozzles and video the mist through a very small hole just large enough for the camera to see through. You do NOT want any outside air to get in or the mist will dissipate too soon. There is a whole lot of guessing with this and it can be hard to judge, but with some practice it gets easier.


Right now my hang time is in the 90 -150 second range depending on my ON time, and air pressure. Shorter On times don’t fill the chamber as much so gives a shorter hang time. It also varies with air pressure as that effects droplet sizes – smaller droplets hang longer.

More on that later, but droplet size has a huge huge effect on hang times. A 10 micron droplet will take 1020 seconds (17 minutes!)to fall 10 ft. A 50 micron droplet takes 40 seconds to fall the same 10 ft, and a 100 micron droplet only takes 11 seconds.

So lets say I'm at 90 seconds hang time to begin with. I would pick an OFF time that is less than that to start with and then let the roots tell you if you are good or not.

By the way - No amount of math will tell you for sure what the right settings are. Always listen to the roots. They will react pretty fast – within just a few hours – and tell you if you have it wrong or right.

When I'm first starting a grow I always over mist at the start. You cannot “over water” in any type of hydro. At the very worst, you will end up with smooth roots. So start out with more than you think you need. Once the roots get growing well, then sloooooowly lower the ON time and increase the OFF time while checking the roots often to see how they like the changes.

Ok, here is a crude drawing of how my system is setup.





That's enough for now. I'm off to bed.

Parts list.

Im only going to list things that are unique to aero.

One of the most important things is the nozzles. These nozzles are not perfect, but they work and they are relatively inexpensive. Im using the Delavan 30609-8 burner nozzles. They run about $26 ea for the bare nozzle. You can also buy an adaptor 17147-1 that makes is easier to attach water and air lines that runs about the same price. I made my own DIY adapters for about $0.50 ea. Im using the brass versions, but there are stainless versions that cost about 4 times as much. I think the brass work fine. I have seen very little corrosion and the nozzles come apart easily for cleaning if needed.


The root chamber is just two 30 gallon fabric grow bags glued together. Cut the bottom out of one and hot glue it to the top of the other one and you have a 24" diameter x 28-30" tall root chamber that will be self cooling. Five for $23 on Amazon.


Its important to keep light and air currents away from the root chamber. The fabric breaths easily and you can see light right through the fabric. Ive enclosed my chamber with a simple box made from 1" thick construction foam from Home Depot. Remember the chamber will stay from 7 to 10 deg F cooler than room temps, so you need to keep the heat in in a situation like mine. If you had the chamber inside a grwo room that stayed closer to 80F, you would need to change the design a good bit. It doesnt need to be well sealed. In fact, you want some fresh air to be able to get in - just be sure its not much air - no breazes. Also be careful NO light cant get in. You will want an easy way to get into it to check the catch basin.

You will also need timers. I am using one timer for each nozzle. These are cheap and so far are perfectly reliable. I see the price has gone up. They were $8 ea


Im using these cheap solenoids. Two or three of these have had issues over the last two years, so I keep a couple of spares on hand at all times. Again, one per nozzle. Note the MINIMUM working pressure is zero. Thats important. I have had them ship me some of them that had a minimum of 0.02Mpa, which is supposed to be about 3 PSI - but those were iffy when trying to run them at 5PSI and even as hi as 7 PSI. So check the minimum working pressure.


You will also need a 12 volt power supply. The solenoids only draw about 5 watts, so it doesnt have to be huge.

You will need an air compressor. If noise isnt an issue, any contractors type compressor will do fine. Im growing in the back bedroom, so I needed a quiet one. They are $140 now, but go on sale sometimes as low as $120.


I also added a second regulator near the solenoids for finer control of the air pressure. The typical ones you find on a compressor are not reliable at low pressure settings.


I use inexpensive Inkbird controllers to regulate the heater for the root chamber. Im just using a little 700 watt personal heater. You will also want inline filters for water and air. You will also need a 12 volt power supply for the solenoids.

These nozzles are siphon type, meaning they suck the water up into the nozzles on each cycle rather than using any pressure. You could use gravity feed, but then you would need another set of solenoids that worked reliably at zero minimum working pressure. Mine do not.

For the siphon tank I just use an empty plastic container - coffee creamer in my case. It needs to be wide enough to fit a float valve. Im using this valve and it fits comfortably in a 5" wide container.


My rez is just a plastic icechest. 3/8" pushfit tubing fits perfectly in the drain hole which makes for an easy connection to the filter and the siphon tank. For filters Im using ones with 200 mesh screens.

You will also need tubing, fittings, wire, connectors, adapters, shut off valves, etc etc to connect all the bits and pieces together.

I almost forgot - you will need a catch basin under the root chamber to catch runoff from excess spray. About 90% of the nutes you spray early on get wasted. Later in the grow, when the chamber fills with roots, more gets used up, but you still will have significant runoff. Im using a plastic water heater drip pan. . I have a drain hose that runs to the outside of the house, but I stupidly made it 3/8" tubing and it gets clogged up easily. Periodically I have to scoop the water out of the tray by hand, then blow the tube clear with the air hose.

That may sound like a lot of wasted nutes, but its really no more than any other hydro where you have to do rez changes routinely. Being able to run at significantly lower EC values, and all the benefits of drain to waste, more than make up for any small downsides.


Thats pretty much everything that you wouldnt already be uesing for any grow.

Enough theory. Time for a root porn up-date.

the roots are doing great. All three root masses are expanding fastest at the top - where the mist is thinnest - and are starting to merge together. They are also starting spread along the ceiling - following the water where it beads up on the top of the chamber.




I am always fascinated by the odd things aero roots do - like loops and cork screws.


All three sets of roots have reached the bottom, but you cant see the third set - they are hidden behind the big baby. You can see there are fewer fuzzy hairs down here and they are shorter. This part of the chamber always has the most mist, so the roots stay a lot wetter and dont develope the same amount of fuzzy hairs.