All COB Users - Lettuce Grow Challenge!!

i am very interested in cobs for aquaponic lettuce..on floating styrofoam rafts..

we already have a test setup using mostly trout

we are using led bars , led panels...they are doing fine..

we want "finer"

the ergonmics of having to put them close is something that would be good toget away

from..though the chinese[cheap] panels can be hung higher..

we are about to order some 4 and 8 ft led tubes..with decent lm/w and cct..BIUT

we are interested in using cobs [ i dunno if i want to give any up for that until i have tried em for cannabis]

i am thinking that the vero 18's or even 3590's ran at 50 w..

and hung like what 30 in high would cover a lot of area for lettuce [it would nice to know how much]

and salad greens so maybe we could space them 24" apart and stull grow good sald?

i am hoping somebody here finds that out.....i somehow wanna stay awy from even custom designed chinese

lighting..because in the end we may get more bang for buck with these expensive cobs

because we can hang them higher and have each cob cover more area because of salad greens being less demanding

this is very pertinent thread for us too

wont be taking them to full harvest under cob's but heres some of my veggies grown under cxb3590's. they were in solo cups until 36 hours prior to these photographs. still too cold to put them outside in northern maine

OLD MOTHER SATIVA said:

i am very interested in cobs for aquaponic lettuce..on floating styrofoam rafts..

we already have a test setup using mostly trout

we are using led bars , led panels...they are doing fine..

we want "finer"

the ergonmics of having to put them close is something that would be good toget away

from..though the chinese[cheap] panels can be hung higher..

we are about to order some 4 and 8 ft led tubes..with decent lm/w and cct..BIUT

we are interested in using cobs [ i dunno if i want to give any up for that until i have tried em for cannabis]

i am thinking that the vero 18's or even 3590's ran at 50 w..

and hung like what 30 in high would cover a lot of area for lettuce [it would nice to know how much]

and salad greens so maybe we could space them 24" apart and stull grow good sald?

i am hoping somebody here finds that out.....i somehow wanna stay awy from even custom designed chinese

lighting..because in the end we may get more bang for buck with these expensive cobs

because we can hang them higher and have each cob cover more area because of salad greens being less demanding

this is very pertinent thread for us too

Click to expand...

Are you using the led's as primary or supplemental lighting?

robincnn said:

View attachment 3675097 View attachment 3675099
They do feel thick "leathery" on top. I also noticed that the roots developed very quickly under the LED and they were coming out of the hole under the pot. needs frequent water too.
View attachment 3675100 View attachment 3675101 View attachment 3675103

Any idea how the spectrum looks like for Hortilux Blue MH

Saw a few research articles for 'Lettuce Spectrum' under google search and google scholar search.
https://www.researchgate.net/profile/Pavelas_Duchovskis/publication/259973431_Optimization_of_lighting_spectrum_for_photosynthetic_system_and_productivity_of_lettuce_by_using_light-emitting_diodes/links/0046352fe59872cc43000000.pdf
https://www.heliospectra.com/sites/default/files/file_file/akron_whitepaper.pdf

Moved one of these to a 3500K tent to see if it does better.
View attachment 3675096

Click to expand...

Hopefully we can get input from enough folks to figure out this lettuce "mystery"
I'm wondering if it is:
(1) intensity (too much?)
(2) Lack of yellow/green in most led spectrums

6" from T5's produces nice stretchless starts

Lettuce requires much less light than plants like tomatoes, about 1/2 as much daily. Also tomatoes and OTHER plants like to be warm when they are growing, lettuce doesnt and tends to bolt sooner if kept too warm. I think for most users, quite a bit of experimentation will be necessary to perfect their lettuce grows. One thing I have discovered in my Kratky units, when trying to adjust the PH, the water needs to be stirred WELL after any nutrients or acid is added cuz they will settle to the bottom and not distribute in the solution. I didnt realize acid would do this and couldnt figure out why my PH wasnt dropping after days of attempted adjustments. Before I stirred it was 6.8, after I stirred the solution it was 3.2! Sooo, I had to dump the whole batch and start over.....

DLI google it

Yes, us green leafers know about 300 DLI. It get's real interesting when you start reading about short day varieties and all the genetic differences.

Krafty makes no sense to me at all. How do you know at any point what is in your nutrient solution unless you own a lab? No thanks, I'll stick with active water movement and regular res dumps to insure no toxic buildups or deficiencies

Not COB lettuce, but LED nonetheless. If thats not ok to post in this thread just let me know... Folgers containers make good single plant hydro units btw. In these Im using rainwater with Jacks hydro fert + calnit plus 2ml / gal magi-cal and 1.5ml/gal of Floranova grow.

thetr33man said:

Not COB lettuce, but LED nonetheless. If thats not ok to post in this thread just let me know... Folgers containers make good single plant hydro units btw. In these Im using rainwater with Jacks hydro fert + calnit plus 2ml / gal magi-cal and 1.5ml/gal of Floranova grow.

Click to expand...

Definitely ok to Post!!
Let's make this the most comprehensive LED lettuce post ever.
What led's are you running?

OneHitDone said:

Definitely ok to Post!!
Let's make this the most comprehensive LED lettuce post ever.
What led's are you running?

Click to expand...

This is a cidly aquabar custom spectrum 660 red, 6500k white, 2700k white repeating, 36" 3w diodes.

thetr33man said:

This is a cidly aquabar custom spectrum 660 red, 6500k white, 2700k white repeating, 36" 3w diodes.

Click to expand...

Please keep us posted as your lettuce matures. Are you going for full sized heads?

OneHitDone said:

robuncnn, I see that you are getting some of the deformation going on on your lettuce leafs. Do they have a thick "leathery" feel to them?


My take away is that lettuce is very spectrum sensitive and I need to do more testing. I am hopeful to find an led solution that will work well in a stacked shelf system so I can crank out some lettuce indoors

I really appreciate you folks in this section of the site. Such great information being shared over here

Click to expand...

So I think some of the leaf deformations may be a result of intensity, though comparatively I think onehit and robincnn have a bit more distance between light and plant. definitely noticing some bleaching and minor burn a note on that - seems that when camera shows preview these areas are indicated as overexposed when pic is taken in auto mode, also emphasizing the importance of what you see may not be what you get because all our cameras are different. Anyone not using auto mode please indicate what settings you are using. This little experiment continues to emphasize the importance of paying attention and using your tools to test and try at very little perceived risk I find it laughable that more people don't do it more (especially noobs). Another thing about intensity, seems that closer seedlings are stretching more - relateable to foxtailing in some instances? I've always wondered if you could eliminate the need for a light mover if you just emulate the entire sky (as perceived by the plant) as a Sun - one big semi-circle led array.

The media transplant baby head lettuce is doing ok now in coco and vermeculite - any suggestions for ph adjusting via non commercial products, also all I have at this point for ph testing is hottub test strip. Lots transplanted, peas, carrots, onions are up.


Oregon peas

Bleaching on baby head

The Basil has a bit of burn, I don't think the lettuce is "leathery" more like baby's bottom (technically leather)


@thetr33man spacing indoors is a big question for me too, I'm tending to throw the package recommendations out the door because the vertical spacing is going to dominate my design considerations.

thetr33man said:

Lettuce requires much less light than plants like tomatoes, about 1/2 as much daily. Also tomatoes and OTHER plants like to be warm when they are growing, lettuce doesnt and tends to bolt sooner if kept too warm. I think for most users, quite a bit of experimentation will be necessary to perfect their lettuce grows. One thing I have discovered in my Kratky units, when trying to adjust the PH, the water needs to be stirred WELL after any nutrients or acid is added cuz they will settle to the bottom and not distribute in the solution. I didnt realize acid would do this and couldnt figure out why my PH wasnt dropping after days of attempted adjustments. Before I stirred it was 6.8, after I stirred the solution it was 3.2! Sooo, I had to dump the whole batch and start over.....

Click to expand...

Some are acid salts that take a while to dissolve particularly in cool water, do you have crystal formation in your acid bottle?

SSGrower said:

Some are acid salts that take a while to dissolve particularly in cool water, do you have crystal formation in your acid bottle?

Click to expand...

No but Im using straight sulfuric acid, not commercial ph down.
SSgrower, non commercial PH adjustment you can use sulfuric acid, purchased at auto parts store as battery acid and for PH up you can buy 100% lye at a hardware store and dilute it in water, same with sulfuric acid. It comes 33% concentrated, very dangerous as is, I dilute it 8 oz in a 2 liter bottle of water. Like that I have spilled it on my skin before and rinsed it off a few seconds later with no pain or damage. When handling the concentrated version be sure to wear rubber gloves and goggles tho.

this thread is cool,, my grow box is empty right now,, hum,, ideas now

thetr33man said:

No but Im using straight sulfuric acid, not commercial ph down.
SSgrower, non commercial PH adjustment you can use sulfuric acid, purchased at auto parts store as battery acid and for PH up you can buy 100% lye at a hardware store and dilute it in water, same with sulfuric acid. It comes 33% concentrated, very dangerous as is... When handling the concentrated version be sure to wear rubber gloves and goggles tho.

Click to expand...

Just to reinforce your point eyes, eyes, eyes, and lungs, lungs, lungs. Bases are as bad or worse, also 33% fuming h2so4? No opposition to others using it just hoping for something a little less "aggressive "


P.s. cant anyone around here spell? Kind of embarrassing to have misspelled lettuce on all my attachments

Has anyone used tartaric or malolactic (sp?) acid for ph ing? These are used in home wine making (yet another fun and frustrating hobby) and in fact for some wines acid salts will precipitate out settle on the bottom the carboy (along with yeast and a bunch of other crap). Also, forgot about the titration kit I have but it reports is % acid vs. some winemaking standard that in some way accounts for the "strength" or oxidizing capability of the acid. I will report back on this I can find a useful conversion or way to apply it, but figured if any knows I'd ask?

update : running72v COB's at 350mA at 25 watts and the leaves are HYuge. lol It seems that lower wattage and higher u/lumens is better for the plants. peace

VegasWinner said:

update : running72v COB's at 350mA at 25 watts and the leaves are HYuge. lol It seems that lower wattage and higher u/lumens is better for the plants. peace

Click to expand...

Dam Skippy sure does seem proof positive better how many cobs?

I have begun hardening of some of my veggies but will continue with some indoors to completion.

SSGrower said:

Dam Skippy sure does seem proof positive better how many cobs?

I have begun hardening of some of my veggies but will continue with some indoors to completion.

Click to expand...

Using two cob's passive heat sinks. peace

Err..... Sarge..