Indoor Hydroponic Lettuce in a Small Space (Yogurt Containers System) Part 2

This is a spill-over post to the first part of growing hydroponic lettuce indoors using yogurt containers.

I have two sets of lettuces going (three in each set). The first set I left one plant to grow passively and did not aerate its reservoir. Instead the plant's roots have grow down into solution and it will get oxygen through its upper roots that are exposed to air. Unfortunately, that plant doesn't seem to be doing very well. 

Here is an update of the plants on their second nutrient change:

All the plants, as of 12/29/13

This is one of the aerated plants

This is the other aerated plant.

Here is the passive one

Here are some new plants I'm starting. They are almost 2 weeks.

The plants seem to be looking good.The root systems are nice and white and long. They aren't growing as fast as I had hoped but that isn't really a surprise. There are multiple reasons why they may be slow to mature.

The lights (60w and 32w CFLs) are probably not as strong as they could be. I may not have been upping the nutrients as fast as I could have (having no TDS meter). Also, there are other nutrients I could have added besides the GH MaxiGro nutrients. The temperatures stay constant via ice packs that are switched out of the bin (the water that the reservoirs are in) daily. The pH is tested with every nutrient change.

It seems like the most likely limiting factors are light and nutrients/timing of nutrients.

I hope that the lettuces will fill out eventually, maybe they'll just take a bit longer to do so. It is only 30 days after all, most lettuces are 45-55 days to maturity.

The yogurt containers are working out well from the standpoint of changing the nutrients though. That was my whole reason for making this system, because I am growing in a space accessible via ladder only and didn't want to have changing the reservoirs be a huge to-do (because then, it just wouldn't get done :  D ).

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UPDATE:12.31.13

I looked at the plants today, growth is pretty much the same it has been. But then roots look a bit odd:

Mold on the roots or just root hairs?

I'm not sure yet whether this is mold or not, but I'm leaning toward mold since there are other lettuce roots which are just white and healthy looking without the tiny white fuzziness. It makes sense since there isn't a whole lot of air exchange/flow from the inside of the yogurt container where the roots are to outside it. The air would have to come up and out through the net pot, which already has the rockwool and hydroton rocks in it. Another thing is that the loft space where the whole setup sits doesn't get the best air exchange either. This will have to be modified in future grows.

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UPDATE:1.4.13

So I changed the nutrients in the inital batch of lettuce for the third time, almost to full strength. In the days after that nutrient change, the plants began to droop a bit and overall just didn't seem very happy. 

Here are some pictures from of the roots:

They look terrible! The roots, which were beautiful and white now look lifeless and brown. I'm not sure why this happened. The nutrient change wasn't a huge increase in nutrient and they had a good amount of time before upping it. I also added some hydrogen peroxide to the new nutrient solutions. Maybe the mold has something to do with it? 

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UPDATE:1.10.13

So I've been busy lately and actually didn't get a chance to look at the plants in a couple days or change out the ice-packs. I figured they were on their way out, after seeing the roots turn brown. But when I went up to look at them today their growth was huge! I was impressed. 

Then looking at the roots I was in for an even bigger surprise....

There are tons of white healthy roots shooting through the net pot!

This one too! You can see the dark older roots still hanging there and then the fresh white roots coming through.

Picture of how big they've gotten. Note the failed passive plant in the lower right/

Here are the second crop, they are coming along well.

I didn't expect the plants to make a comeback like that, but it looks like they did! I guess they just needed time to get through whatever made the roots do that. It's good to know that plants can be so adaptable and responsive like this! I will do one last nutrient change and then after that likely harvest them.