Advice, Opinions on this Tray Ebb&flo/Dwc System

Hey all... I'm hoping to get some opinions on my grow in multiple 4x8 ft grow trays.
What im doing is using these trays enclosed with a signboard lid . Cut holes out for 4" mesh pots stuffed with 3.5" RW cubes. The pots are suspended in the tray by the lid. In turn the lid sits on the tray edges and has support legs mounted under the lid to prevent it from bending under the weight. Theres about a 2" gap between the bottom of pot to the tray bottom.
Heres the thing... Im not using any grow medium in the tray ! Other than the RW in the 4" pot to veg the plants.
So far their in week 2-3 of flowering and doing fine. I think.... Im concerned with root bounding etc.
Have 2 60gal reservoirs at 65F. Watering two trays at a time takes 4min to fill. Then 6 minutes to drain. Then the other two trays do the same and the cycle starts all over again.. So watering cycles very tight. Have aggressive aeration with large air pumps and stones as well.



Here is the clone tray I made. 150 clones go in this for up to 3 weeks. Then I remove them and they goto flowering room. In there each 4x8ft tray holds 36 plants and under 2 1000w hps on light movers per tray.



Hers the Purple kush clones at week 3 being pulled for transplant. Root entanglement was manageable... Most were 18 to 20" tall by this time. And very healthy..


Heres the roots in week 1.5.



1st week in flowering. bottom trays.

Top trays...



At end of week 2. Alls well.

Getting into week three im starting to see some signs of root problems. The smaller weaker clones yellowing bottom up. With root rot of varying degree.
Im culling those plants but am wondering if this will happen to more of them? Or even all of them because im not using a grow medium or something !!
Anyone out there have experience with this type of setup? Or even good advice? I'm worried....
More pics available in my photo albums if u wish to see more.
https://www.rollitup.org/members/coreypkgrower-331373-albums.html

I just looked at all of your pictures. what an awesome fucking setup!

why did you choose to go with a sign board with holes cut in it? for stability of the plants? so you could use less media? (medium? sp?)

Also... what type of nutrients are you using? orgainic or inorganic? Do you have any pictures of the root rott? This needs to be dealt with immediately because it's going to spread to the healthy plants for sure. Smaller weaker ones always show the first signs, but it's a bitch to battle.

had a very similar setup on smaller scale, 100% perpetual i harvest and transplant in one day12/12 all along, it produces very fast that i switched since it was for personal nothing more. it's awesome for max efficiency, in hot summers i used to switch flood/drain because more heat tolerant and it seemed insane to run a 1kw a/c for 800w of light, i'd rather use 1kw more of light in cold weather and skip growing for the summer, but in your scale a/c chiller or watever makes perfect sense. i also used grorock, dont like to keep rw saturated especially in early days of growing, and for lid i used pvc board with foam board. your setup is great, i'd make some walls around plants for less light spill

YaK said:

I just looked at all of your pictures. what an awesome fucking setup!

why did you choose to go with a sign board with holes cut in it? for stability of the plants? so you could use less media? (medium? sp?)

Also... what type of nutrients are you using? orgainic or inorganic? Do you have any pictures of the root rott? This needs to be dealt with immediately because it's going to spread to the healthy plants for sure. Smaller weaker ones always show the first signs, but it's a bitch to battle.

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LOL... Thanks YAK. Took awhile to make it all. Well the sign board is called Komotex. Its a internally porous 1/8" thick sheeting. Light weight and fairly rigid. Mold resistant and 12 bucks a sheet ! I cut 1.5" pvc pipe into 3" lengths, split into 4 pieces and glue about 20 to the bottom of each lid for the support. Pvc to pvc cement is an awesome bond and will never break. The pots are supported by the lid. They do not touch the bottom of the tray.
Im trying to avoid using Rock wool, good stuff but pain in the ass to drain and dispose. Clay pellets, lava rock etc. is dirty, dusty, heavy, and non recyclable on this scale at least.
So I thought... Why not just flood and drain suspended plants with no medium and use quick flood and drain cycles...
Using GH nutrients. Three part. Micro, grow, bloom. Also cal mag additive. No other funky shit thou. Keep it simple. Also H2O2. Rate 4ml/gal. Replenish at a rate of 20% loss per day. Reservoir clean and change out weekly.

zem said:

had a very similar setup on smaller scale, 100% perpetual i harvest and transplant in one day12/12 all along, it produces very fast that i switched since it was for personal nothing more. it's awesome for max efficiency, in hot summers i used to switch flood/drain because more heat tolerant and it seemed insane to run a 1kw a/c for 800w of light, i'd rather use 1kw more of light in cold weather and skip growing for the summer, but in your scale a/c chiller or watever makes perfect sense. i also used grorock, dont like to keep rw saturated especially in early days of growing, and for lid i used pvc board with foam board. your setup is great, i'd make some walls around plants for less light spill

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Thanks for the feed back ZEM... Ya in the summer months my 24,000 btu A/C units barely do the job. So reduce to just 4 lights during that time.
I have found the reflectors in the light pipes do a great job keeping the light on target. Very little spill. Have only to small back walls exposed and not want to paint them and can stick poly on them. Falls off after awhile.
I have 2" foam board under all the trays and all the sides insulated and covered to keep the cool in. I modified a Danby 7800 btu AC unit to cool the nutrient. Works great !

Geezz... Just as I suspected. Root rot is starting. I just spent a few hours root trimming the most obvious plants. Some had to be completely stripped of roots. Shit fuck !!!
They were healthy when the went in there. plants grew great and tripled the root mass in the following two weeks. But now looks like there's a problem. I did not change anything and nothing mucked up either.
I'm thinking there is not enough O2 in the nutrient. Once the plants roots get to a certain size the O2 required exceeds my ability to replenish with 2 60gal tanks with pumps and air stones. Root bounding does not seem to be a problem. Its dense but
not tightly packed. The only change was the plants getting bigger and needing more food, water and o2...? Maybe why this is happening.
I changed my controller to now wait 15 minutes between watering cycles. Maybe more air time on roots would help. Cant use more than 5ml/gal H2O2 so Im maxed on that already.
Any opinions??


GF cleaning out the other area... lol

this type of tray requires many airstones, the entire water surface must be bubbled, you can skip the waterpump altogether, only use it to top your res and maintain water level. you're mixing flood/drain with DWC. i keep roots 1/2 submerged and 1/2 suspended in the moist air. try growrock next time, the rot could have started in the RW cubes being always saturated. your res temps are good, must be clean, i don't know why you cant use H2O2, if you're organic, look into beneficial microbes...

I am using H2O2... "Cant use more than 5ml/gal H2O2 so Im maxed on that already." No the rot has started around the middle and lower root bundle. The roots out of cube are fine. Yes I could have just put RW in the trays. Have done that with this system and worked fine. Like i said. Trying to experiment with no medium is the punch line I guess. Would never fill trays with rock, clay pellets etc. Way to dirty, hard to clean and filter etc.
I'm picking up an O2 test meter tomorrow. Going to test water with H2O2 in the system and then refill tanks, run for a few hours and test O2 levels again. I just need to determine if O2 is really the problem.
I'm pumping 34 CFM into 10 airstones right now. Its very turbulent.
Anyways. If this fails. I'll go back to RW for awhile.

Corey... i was reading the thread "it's a fuct world" and in that thread AlbFuct says that plants can easily handle a dose ten times what he recommends. I searched for his post over yesterday but couldnt find it... it's there though! I'll assume that since you're dose is 5ml that you are using 50% grade? I would research this and up the dose. I use 29% and I've put 500 ml, in a 100L res (probably only has 90L when full, or approx 25 gallons since I dont fill it to the tippy top.

Your experiment sounds feasible to me! Hopefully someone else with a little more experience will chime in... but it seems to me like it's an issue of playing with the timings. The pathogens should be able to be taken care of with the H2O2, If your timings were that far off, it seems to me like the plants would show signs of over watering instead of pythium. Since they dont show signs of over watering, maybe your timings are fine.

I do flood and drain and have never used air stones, my rockwool saturates, then dries out. Giving the roots oxygen, then the cycle happens again the next day (once per day is all I flood any of my plants). I'm just thinking out loud, but I don't think that the root rot is caused by not enough oxygen.

First item at hand here is get rid of the pythium. I will try and find his post on dosages when pathogens are present (and not just for maintenance).

**take this with a grain of salt, but if it were me, I'd back the timings off a bit, keeping a close eye on the roots so they dont dry out completely, chill the water maybe a couple degrees more, research and turn your chiller down to the lower end of the variance as far as how cold the water can be, root rot will have a harder time surviving on the colder side of the water variable, and at least double the dose of the H2O2 to handle this root rot!

Again... this is all me thinking out loud as if it were my setup, those plants look so good, pythium is fucked. I really hope you can get this remedied. I'll go look for Al's post again, as I'm sure you need to up your dose and knock out the problem!

p.s. those are the tightest shorts I have ever seen! niiiiiice. niiiiiiiice.

found it! it's on page 39... figures, because yesterday I stopped looking at page 37. lol

https://www.rollitup.org/hydroponics-aeroponics/399206-its-fuct-world-39.html

now i'm off to search for what your water temps are, and what the lowest temp you can go and still be okay is. (I should know these things, but with my system it just doesn't matter much)

a quick google search found this: http://www.marijuanagrowing.eu/water-temp-for-hydro-reservoir-t18372.html

and this: http://www.howsitgoineh.com/forums/index.php?action=printpage;topic=8830.0

and this: https://www.rollitup.org/hydroponics-aeroponics/399878-lowest-water-temperature-2.html

and this: http://www.marijuanagrowing.eu/water-temp-for-hydro-reservoir-t18372.html


seems like you can lower the temp quite a bit, to help with the root rot, then bring it back up when things are healthier.

again... just a suggestion.


Can you post some pictures of what the infected roots look like? are they totally encased in slime? is there still some white poking out? I've dealt with root issues like this way back when (all of 2 years ago..lol). I'd like to see them to know what stage they are at.

YaK said:

Corey... i was reading the thread "it's a fuct world" and in that thread AlbFuct says that plants can easily handle a dose ten times what he recommends. I searched for his post over yesterday but couldnt find it... it's there though! I'll assume that since you're dose is 5ml that you are using 50% grade? I would research this and up the dose. I use 29% and I've put 500 ml, in a 100L res (probably only has 90L when full, or approx 25 gallons since I dont fill it to the tippy top.

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WOW !! 20ml per gallon !! U didnt have any problems? Yes I'm using 29 or 35%.
So Al recommends..." The dosage for 50% grade is 1ml/L. 50/29=1.72 so for 29% H2O2, use 1.7ml/L. " Yup. Thats definitely alot more than I'm using. Most everywhere I read about H2O2 gives a max of 5ml/gal. Maybe thats more for a normal healthy system. Well I dont have anything to loose so I'm going with steroid levels of H2O2 ! ! lol.

YaK said:

Your experiment sounds feasible to me! Hopefully someone else with a little more experience will chime in... but it seems to me like it's an issue of playing with the timings. The pathogens should be able to be taken care of with the H2O2, If your timings were that far off, it seems to me like the plants would show signs of over watering instead of pythium. Since they dont show signs of over watering, maybe your timings are fine.

Click to expand...

Well who knows the best timing on this type of system. I have altered the timing to allow 20min. dry time between cycles now. Lifting some pots revealed roots still damp. I think I will stay with that for a bit.
No over watering signs at all.They were kicken butt for 2 weeks then began to slow... Then the smaller plants began to show nuit deficiencies. The classic sign of root trouble when you know the nutrient is fine. Thats why my theory of lack of O2 occurs as the root mass becomes larger and requires more and more...
Actually... The plants do not wilt when lights come on or any time while the lights are on. I sacrificed 1 plant to check stem for Pythium. The razor blade cut stem was perfect in color ! Of course Pythium will take hold soon enuf if I dont fix this.

YaK said:

I do flood and drain and have never used air stones, my rockwool saturates, then dries out. Giving the roots oxygen, then the cycle happens again the next day (once per day is all I flood any of my plants). I'm just thinking out loud, but I don't think that the root rot is caused by not enough oxygen.

Click to expand...

Well I wont disagree with you there. Its my assumption O2 is the problem. Lord knows the water here is very poor. Lots of minerals etc. If you fill the bath tub with it theres a brown color thats obvious. Yet the PPM is 100 to 110 depending on the season. And small amount of chlorine odor.
I'm also finding it interesting that my Ph is fairly stable right now in the reservoirs. It only goes up from 5.8 to 6.0 in a 12 hr period. Its calibrated weekly and have 2 tri-meters showing same result... Interesting... Would expect higher fluctuations with substantial root rot.

**take this with a grain of salt, but if it were me, I'd back the timings off a bit, keeping a close eye on the roots so they dont dry out completely, chill the water maybe a couple degrees more, research and turn your chiller down to the lower end of the variance as far as how cold the water can be, root rot will have a harder time surviving on the colder side of the water variable, and at least double the dose of the H2O2 to handle this root rot!

Click to expand...

No I think its GREAT advice !! It also makes sense to me and thats the most important part about taking advice I think.
So I will drop temps to 62-64 range. Go with 15ml/gal of H2O2...for now. Increase dry time. See what happens.

p.s. those are the tightest shorts I have ever seen! niiiiiice. niiiiiiiice.

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LOL !! OMG ! yes. Love having her helping sometimes.

YaK said:

Can you post some pictures of what the infected roots look like? are they totally encased in slime? is there still some white poking out? I've dealt with root issues like this way back when (all of 2 years ago..lol). I'd like to see them to know what stage they are at.

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Yes I'll try to take some pics. There in the dark cycle now for the next 10hrs. So tonight I will post some.
The roots I got rid of were not slimy at all actually. Just alot of light brown mixed with some white ones. Yet they crumbled and pulled away fairly easy. I think the H2O2 was doing its job preventing excess rot slime etc.
Thanks so much for your feed back Yak ! The links were very helpful, as was your opinion !

Well I managed to get some pics of the roots. Most plants I couldnt get out of the holes. So I lifted the tray lid to snap a few pics...


They dont look too bad really. A bit tanned but not brown at least. Maybe the H2O2 is keeping things in check...



This one was probably the darker of the ones I checked. The plant is still green and healthy thou..

If there is any root rot there, I am NOT seeing it. that's great news! I wish I could see pics of the plant that you had to cut all of the roots off of..... DOH!

I was expecting a horror show but those are nice fattie root masses. from the pictures, I dont see any signs of root rot at all, just slight discoloration. maybe that's the GH micro? I dont know, as I only see my roots after harvest, and they are not bone white, mostly just the color that yours are, with some newer stark white ones here and there.

is this your first run doing it this way? with such little media? I believe you will make it work, and work well!

I love the idea of little to no media, but hate the idea of not having my plants mobile so I can rearrange them to maximize the lighting.

I'm a big fan of your style and setup... please keep us all posted on the progress from here on out!

YaK said:

If there is any root rot there, I am NOT seeing it. that's great news! I wish I could see pics of the plant that you had to cut all of the roots off of..... DOH!

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Ask... And ye shall receive.. lol



Heres one of the 20 or so I cleaned up the roots or completely striped them away. You can see the yellowing progressing upward. I left only a small amount of root. Surprisingly. None are wilting after or while the lights are on.



Its mostly in the upper trays this happened. The only reason is The best clones were placed in the bottom trays. The top has the average to fair plants.

YaK said:

I dont know, as I only see my roots after harvest, and they are not bone white, mostly just the color that yours are, with some newer stark white ones here and there.

is this your first run doing it this way? with such little media? I believe you will make it work, and work well!

I love the idea of little to no media, but hate the idea of not having my plants mobile so I can rearrange them to maximize the lighting.

I'm a big fan of your style and setup... please keep us all posted on the progress from here on out!

Click to expand...

Thank you. And yes this is the first time. I used RW, Clay pellets, lava Rock b4. They all worked but such a pain to clean up and or dispose.
Glad you think my roots seem ok. Yes there are a few white ones here and there too.
I'm using a custom made light mover. It moves all my lights in groups of four. I have excellent coverage this way and don't feel the need to move them.
However... One could set up this system to allow for moving them around too.


This kinda shows the Light assy..

Ok !! Will keep this updated and start a grow Journal as well.. Thanks again !!

Well four days in and things are looking up. ! Yellowing has stopped and some of the plants I striped roots off are starting to sprout new roots... Sweet !
I'm at 15ml H2O2 / gal. And its definitely working well. Ph has now stabilized at 5.9. Roots that were slightly brown are clearing up as well.
Bud is really starting to pack on some weight now. 3and a half more week to harvest !
Now I just need to figure out what the replacement ratio of the H2O2 is. B4 I was using 5ml/gal and replenishing at 25% per day. With these high levels I wouldnt think it would be 25% any more...
Anyone have any thoughts on this ??




Looken gooood...