February 4, 2010 by Peat
The Lettuce 'Raft' Type System
Basically; cut out six holes in styrofoam or polystyrene and mount your 2 inch net pots. Lettuce seeds are planted in rockwool (or your preferred medium), put in the net pots and surrounded by hydroton. The whole 'raft' floats on the surface of the water, an air pump provides the necessary oxygen to the roots.
I'll be growing this with my 90 watt UFO LED light in the new grow room.
Weekly Pictures (Click to Enlarge)
Fri, 02/05/2010 - 14:06
#2
That's completely true, it's the action of the bursting bubbles which disturb the surface and allow oxygen in. If the bubbles are small enough though, they will impart some oxygen into the tank.
I don't think I'd want to leave the air stone out, without it the plants will use up all the oxygen in the stagnant water, plus, the stone has the benefit of preventing water born diseases. If you think about it as well, the bubbles will be bursting all around the net pots breaking the surface here and allowing oxygen into that area, right around the root ball. 
Sat, 02/06/2010 - 08:00
#3
Week 0 - Starting Week, Saturday 6th February 2010
Here it is then, the lettuce raft using my 90 watt UFO type LED grow light.
Planted at the back left and front right are Tom Thumb Butterhead Lettuce, all the remaining four are a mixed lettuce seed - something along the lines of the AG standard ones.
The container has 15 litres of water in it, I'm using the General Hydroponics Flora 3-Part Series (Flora Micro, Flora Grow & Flora Bloom). The EC is 0.8 and the pH is 6.0 on the seedling mix, lighting cycle is 14 hours on/ 10 hours off. There are two air stones running below the surface and the light is 12 inches away from the plants.
Let's see how the LED gets on then... 
Sat, 02/13/2010 - 04:15
#4
Week 1
All the lettuce has germinated.
Changing the feed to the GH Mild Growth Phase: EC 1.2 and the pH adjusted to 6.0
Fri, 02/26/2010 - 16:27
#5
I'm extremely hacked off at this moment in time, my LED has decided it does not want to illuminate at all in the centre - the only ones now lit are the outside ones and a small handful of others! 
So much for reliability and having a life of close to 7 years! I've used my model for probably less than 4 months, it was not a cheap China import either but cost a fair bit of money for a supposed quality product!!!!
Oh well, there goes my lettuce raft experiment under LED then - I don't think the remaining light will do much for the growth, even less when it gets sent back for repair. If there was an icon for very, very angry then it would appear several times after this last sentence.
Fri, 02/26/2010 - 16:47
#6
So we've both had LED lamps die. Best of luck getting it replaced swiftly. Did they really ask for it back to repair it? Or haven't you had this negotiation yet?
But - are you sure it wasn't a "cheap China import"? I haven't seen any LED lamps that weren't manufactured in China. Or was the keyword there 'cheap' ? 
They're flipping expensive, and yeah, no reason at all to believe in 7 year lifespan. The LEDs themselves, sure, but not the circuit boards!
Fri, 02/26/2010 - 16:58
#7
They go on about being built for the UK market with quality components, but, you can only take this on face value and have to trust the company.
I e-mailed them late this afternoon, hopefully I'll get some reply next week. The policy over here is for repair, not replacement unfortunately, if the product fails after something like 6 months - you only get replacements, or your money back, if it's dead on arrival or fails quickly.
I'm hoping this is a one off and I can look forward to this light lasting a good many years to come, this of course remains to be seen...
Fri, 02/26/2010 - 17:09
#8
HTGSupply kindly just sent me a new lamp, without my mailing them back the partly-dead one. Very nice.
They're not going to repair that, Peat. The LEDs are soldered into a printed circuit board, I think, with resistors sprinkled in. I think the only reliable way to repair that would be to detach all the components (tedious and damage-prone), then solder them (with fresh resistors & whatnot) into a new board. Which would generally be more expensive than replacing the board with all components. 
It's kinda maddening, at least in the US, how you simply can't get electronics repaired, because the labor so exceeds the replacement cost. I had a wonderful LCD monitor whose power supply glitched. Should be a simple thing, to replace the power supply. But no... Such a waste.
Fri, 02/26/2010 - 17:25
#9
It also depends on how they've designed the thing, could be they use specific chips to drive chains of LED's, one chip would power one chain with another supplying the next chain. It may be as simple as plugging in a new chip, but, who knows what's inside - I'd have a look, as I'm want to do, but this would void the warranty.
I would much prefer a replacement model as I'm not too keen on repairs, I hope that's what I''l get.
Sat, 02/27/2010 - 04:32
#10
Week 3
I'm not sure what's going to happen to these plants now, if a get a new light then they may recover. If I have to send it back then there'll be no light at all, unless I rig up my CFL on them which will be a little tricky.
The LED picture is heavily pink due to the inbalance in the lights.
Compared to my aero unit they've lagged behind, I'm unsure whether to blame the LED or this method of growing. Without a direct comparison of LED vs CFL then I'll have to sit partly on the fence, with one leg dangling into the 'I'm unsure of this/my LED' camp.
Sat, 02/27/2010 - 12:13
#11
My guess is they'd take off with a CFL. It's a shame, though - with a 90W LED, I thought they'd do well.
Sat, 02/27/2010 - 13:55
#12
They should have grown really, really well.
I'm basing this on the experiments over at the Hydroponic Workshop site, the one we've both seen. He grew his under his 90 watt UFO (using an aero unit such as mine though, not the raft), his exploded in growth, very impressive results actually.
Now, is it my LED or the raft method at fault here? Hmm. 
Sat, 02/27/2010 - 17:32
#13
(A link to the 'Hydroponic Workshop site - ~4 weeks from seed' Pete referred to. I think.) (And his UFO specs at the beginning of the experiment.) I think Pete and I discussed this in email last time.
Interestingly, his LEDs more closely matched mine than yours in specification -7:1:1 red:blue:white.
Mine do grow plant, no question. 90W of them should grow more plant faster. That wasn't the question I was trying to answer though. I was trying to find whether head-to-head, watt-for-watt, LEDs grew enough better than CFLs, that I could add aesthetic color-correction lamps and still grow more for less energy with LEDs. If I'd picked a less classy CFL, the answer might have come out differently. (Aerogarden bulbs are actually cheaper now than the CFLs I picked. Not the same Kelvin. But I wanted the best possible growlight CFL in spotlight form for nearly identical wattage...)
You still have the lights on, right? Would it be difficult to add a lamp to your rig with a plain old CFL bulb? Just to enrich the light on your greens.
Sat, 02/27/2010 - 17:36
#14
P.S. Is the UFO kinda hot? You said it burned your cucumber plant. I'm not seeing a lot of difference in temperature between CFL and LED - latter only slightly cooler. I wonder if the heat is weakening the soldering. I wouldn't think so, though, right? Most electronics generates heat.
Mon, 03/01/2010 - 13:32
#15
The UFO is only just warm when you touch the LED glass, nothing to worry about here. The cuke got burnt because the top of it was virtually touching the unit, there is so much light coming out of the thing that the problem, as far as I'm aware, was due to the sheer intensity of it - light burn if you wish.
Funnily enough, the plants are still growing OK, perhaps what little light I have is still doing the job?
Tue, 03/02/2010 - 17:01
#16
Week 3 + 3 Days (Change of Light)
The company wants the UFO back to see what the problem is, that means I'll definitely be left with no light. So, I've put the 125 watt CFL (6400K spectrum) in there now, at least I won't lose the plants.
Until the change of light today, the plants haven't grown too badly since the last picture 3 days ago!
Tue, 03/02/2010 - 18:58
#17
Yeah, they're perking up a bit. Still only so-so for 3.5 week greens, but I gather a lot of them aren't lettuces.
It's strange that they had slow growth instead of attenuated growth. Not-good light should have made them leggy. Slow growth probably may have more to do with what's underneath the raft.
Sun, 03/07/2010 - 03:52
#18
Week 4
After nearly removing the whole system when the LED went down, I'm now much happier after the CFL I put in has started producing the goods. I think one more week should do it before I can start cutting some of these leaves off - Gisette, if you spot corn salad let me know 
I've now upped the nutes to the full GH growth stage (complete water change), I should have done it earlier in the grow but I wasn't sure if I wanted to continue on with this - I will now.
GH Full Vegetative Growth Stage: EC at 1.2 and the pH is 6.0
Sun, 03/07/2010 - 12:21
#19
Now that's growing much better, like lettuce should!
And everything I see in there is lettuce, Peat. Maybe the brassicas are hiding. 
Sun, 03/07/2010 - 12:23
#20
They're just awaiting their turn after the lettuce goes first.
Sat, 03/13/2010 - 11:01
#21
Week 5
It's a jungle in there!
Last picture of all the growth before I start cutting most of it down, I want to develop the Tom Thumb butterhead's at the back left and front right - things are a little crowded at the moment.
Some of the tall lettuce at the front is a little burnt due to the light, it got too tall for it's own good. It's a shame the LED failed as I wanted to see what it could do, a grow for another day...
GH Full Vegetative Growth Stage: EC at 1.2 and the pH is 6.0
Sat, 03/13/2010 - 11:27
#22
Looks delicious, Peat.
I'm growing a pod of Tom Thumb for the first time now. Does it not work for cut & come again? Or do you really want a head.
Sat, 03/13/2010 - 11:56
#23
Thanks.
I'm going for the full head with this one.
Wed, 03/17/2010 - 12:28
#24
Week 5 - Some trimming back!
Plenty of cutting back carried out to free the butterheads, the lettuce harvested tastes very good - the low EC has suited this well.
The butterhead at the front is forming well, the one at the rear seems confused as to what to do - shall I form a proper head or just grow individual leaves?
Oh, the tip burn is due to the lights and not me mixing up the wrong strength nutes.
Wed, 03/17/2010 - 12:40
#25
Yumm.
Do you expect the cut-back lettuces to grow back?
Wed, 03/17/2010 - 12:51
#26
Perhaps? It was a severe cut so I'm unsure if the come again lettuce has enough 'come again' to regrow.
The butterhead has a cropping period of 65 days (9 weeks), I'm hoping they will exceed this. Once they are pulled then it's the end of this project - the come again therefore has the remaining weeks to do something...
Wed, 03/17/2010 - 20:09
#27
I'm glad you mentioned that about tip burn, btw, Peat. I do think 1.7 is a fine EC for my bibb and romaines, but if I miss a few days topping off, it gets a tad more concentrated, and the tom thumb butterhead really does seem to feel it first.
I'm not letting mine head, though. It's awfully good!
Sat, 03/20/2010 - 04:30
#28
Week 6
The two butterheads are coming along fine, plus, there is regrowth in the ones I cut back - notice the basket front left.
GH Vegetative Growth Stage: EC at 1.2 and the pH is 6.0
Sun, 03/28/2010 - 08:41
#29
Week 7 (End of Grow)
I've decided that the Butterheads are big enough for me now and I've taken them out of the system, the other lettuce that I cut back is not too impressive so I've ended this particular project. I now have to clean/bleach the whole lot, raft, container, hydroton and net baskets... how I hate the end of a grow.
The Butterheads are quite big, over 12 inches in diameter and taste very good - I'm pretty happy as this was nearly a non-starter due to the LED failing.
So, there you have it - 'The Lettuce Raft' system, a good way of growing lettuce in particular, simple to build and simple to maintain.
Here are the two Butterheads, as usual, click on the picture to enlarge.
Sun, 03/28/2010 - 15:48
#30
Yum.
Know what you mean about mucking out after a grow....
Looking forward to this, Peat!
Someone said (Joyce?) that air bubblers only oxygenate water by the bubbles breaking at the surface. I don't know that this is true. But if it is, I wonder if floating the raft would frustrate aeration by bubbles.