Gauging Misting Frequency or length through a grow?

Hi, I'm new here and to aeroponics. I've been growing for a couple years. Soil, then DWC. With covid lockdowns I thought I'd try my luck at aeroponics. My last 2 grows has been "aeroponic"; Not sure it's "true" HPA, as I just did was use the "mist king" kit and pump directly to totes(with the timer triggering the pump), no accumulator tank and solenoid. My more recent understanding for the sole+tank, is primarily not kill the pump prematurely, but when I was getting into aero, information was scarce or my google-fu is failing me. My local hydro store wasn't much help either. Attached is the first grow's roots, but didn't take second grow's photos because I was overloaded at the time, but they appeared more like long tangled dread locks(guessing over-fed them, though didn't see any signs of nute lock out).

I have attempted to search this topic, but like I said above, most things aeroponic info is scarce, so it's more me flying around blind.
I'm curious if there is a "scientific" way to determine an ideal rate/timing during a grow cycle? Like a hygrometer probe? I suppose my first grow was better because I was constantly guessing the timer/rate, whereas my second was more complacent due to my schedule. Any tips or suggestions is welcome.

Related question: Whats the nute consumption rate you guys are seeing with your aero grows? Obviously everyone's will be different, but in 2x 27 gallon totes(4 plants total), I was doing at least 60 litres of water a week.

Its hard to tell with that odd lighting, but those roots look pretty good to me! Were they fuzzy or smooth? Im surprised they look that good based on your description of your system setup.

Unfortunately there is no way that I know of to measure mist levels and use that data to automatically adjust timing. You need to use your mark one eyeball and just look at the roots and see how they are doing.

Its easy to tell if you are running too dry - the roots will air prune and die back. Its much more dificult to tell when you are at the goldilocks level of just right.

My personal standard is getting pure white, very fuzzy aero roots like these.



Timing is all about giving the roots just enough mist without giving too much. Its all about maximizing aeration. Too much water reduces the amount of O2 the roots get, but too little water and they die back and air rpune.

You cant really over mist in aero. At the very worst case - assuming you have everything else under good control - you will end up with smooth roots. Smooth roots are not bad roots - BUT - fuzzy roots are better. Fuzzy roots are the best you can hope for as far as roots efficiency in nute uptake and O2.

There is way to much info for me to try to re-type it all here, so let me point you to a couple of recent threads where Ive gone into a lot of detail on aero setups in general.

etcher said:

Related question: Whats the nute consumption rate you guys are seeing with your aero grows? Obviously everyone's will be different, but in 2x 27 gallon totes(4 plants total), I was doing at least 60 litres of water a week.

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I currently grow AA aero - air atomized. I did HPA, LPA, and all sorts of other hydro options in the past. Anyway, I only do drain to waste, My root chamber is aprox 56 gallon fabric pot. Waste water is collected in a drain pan under the pot.

In my most recent grow, I started out at an EC of 0.3 and a flow rate of 2.8 liters/day. By the end of the grow I was up to an EC of 0.5 and a flow rate of 3.2 liters/day thru most of flower with a final increase to 3.9 LPD for the last 2 weeks or so. As my root chamber fills with roots, its necessary to increase the flow rate mostly to over come areas that are blocked by the root mass. Aero roots are very good at growing toward nozzles.

Larry3215 said:

Unfortunately there is no way that I know of to measure mist levels and use that data to automatically adjust timing. You need to use your mark one eyeball and just look at the roots and see how they are doing.

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That's a bit disappointing. I wasn't necessarily looking for an automated system. I was thinking hypothetically, using a hygrometer probe inside the growth chamber and a stop watch, and timing when RH inside the grow chamber fell x%, to use that as a basis for my timer for that week. Was just curious if this was a known number.

Larry3215 said:

You cant really over mist in aero. At the very worst case - assuming you have everything else under good control - you will end up with smooth roots. Smooth roots are not bad roots - BUT - fuzzy roots are better. Fuzzy roots are the best you can hope for as far as roots efficiency in nute uptake and O2.

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Yeah, mine were fuzzy and were white, until flower period. Both grows. The more recent grow the roots pooled out and around the bottom of the tote. I was doing drain to waste, but basically the the roots were eating the waste near the drain by the time of harvest. And apologies for the light cast. So... feeding them less often the "air pruning" will kick in and this will likely be less of an issue?

Larry3215 said:

There is way to much info for me to try to re-type it all here, so let me point you to a couple of recent threads where Ive gone into a lot of detail on aero setups in general.

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I'm very appreciative of the links. Prior to coming across to Rollitup, I found so little info on other boards like 420mag, etc. But this forum the info does seem extensive. Don't think I've come across AA until here. Now you have given me new goals . No, going to keep trying to refine HPA first, since I'm being shamed by my current method

Larry3215 said:

In my most recent grow, I started out at an EC of 0.3 and a flow rate of 2.8 liters/day. By the end of the grow I was up to an EC of 0.5 and a flow rate of 3.2 liters/day thru most of flower with a final increase to 3.9 LPD for the last 2 weeks or so

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I'm jealous. Extremely jealous. Definite goals. Whats your power draw on this kind of setup? I've just been using a PureSine UPS in the event of a power outage. Not connecting the lights or exhaust, just the pump and timers.

Larry3215 said:

Aero roots are very good at growing toward nozzles.

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Yepppp... I found the same, almost to a detriment. I'm going to try rotating my net cups every day or so, but I also scrog, so that might only work for so long.

etcher said:

I was thinking hypothetically, using a hygrometer probe inside the growth chamber and a stop watch, and timing when RH inside the grow chamber fell x%, to use that as a basis for my timer for that week. Was just curious if this was a known number.

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You will find the humidity is always right at 100%. It pretty much cant drop because you have all those wet roots and droplets floating around and on the walls, floor, etc. The humidity wont drop enough to measure until its way too late.

etcher said:

So... feeding them less often the "air pruning" will kick in and this will likely be less of an issue?

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I think if you do that the plants will just not grow as well as they could. Better to give them what they want, and do your best to keep the nozzles free. I often have to reach into the chamber with my hand and move roots over away from the nozzle. I also can rotate my nozzles and raise them up/down to change the mist direction. Still, if you have a long grow and/or a relatively small or crowded chamber, its going to be a fight.

etcher said:

No, going to keep trying to refine HPA first, since I'm being shamed by my current method

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AA and HPA are very close. They share most of the same issues and are virtually identical as far as plant health/growth etc - assuming both are done correctly.

etcher said:

Whats your power draw on this kind of setup? I've just been using a PureSine UPS in the event of a power outage. Not connecting the lights or exhaust, just the pump and timers.

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3 Timers, 2 solenoids, 4 Inkbird controllers, 1 aquarium pump in the rez probably draw a total of 3 amps maybe? The air compressor is around 6 amps maybe? That doesnt include 2 fans and two heaters. The fans are probably another 3 amps and the heaters 1500 watt and 750 watt, but all of these are only run intermittently based on the inkbird settings. You could easily do without the fans and heaters for a short time.

etcher said:

I also scrog, so that might only work for so long.

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I love scrog, but it does limit things you can do.

Larry3215 said:

I think if you do that the plants will just not grow as well as they could. Better to give them what they want, and do your best to keep the nozzles free. I often have to reach into the chamber with my hand and move roots over away from the nozzle. I also can rotate my nozzles and raise them up/down to change the mist direction. Still, if you have a long grow and/or a relatively small or crowded chamber, its going to be a fight.

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I should have added one more thing - you can reduce the roots tendency to grow sideways towards nozzles by increasing the flow rate. Higher mist levels/cycling more often, etc will keep the roots wetter. When water droplets form on the tips, the root will try to grow "toward the water" - which is on th e tip in this case. That results in the root growing down instead of sideways. You will have fewer fuzzy hairs, so its a trade-off situation.