I recommend "Gardening Indoors with Soil and Hydroponics" by George Van Patten. Great info.

Lettuce is very simple to do in a raft. Fill a tote or bucket up with water. Add nutrient. Place an air stone in there for added oxygen. Cut holes in something that floats on the surface and can support the plants. Place the net cups or whatever you use to hold the plant in the holes. Watch them grow and harvest a month later or so. Make sure to use lots of light and keep the temps down. Cooler is better for lettuce and most other greens.

Thanks Joe for ur feedback..

Ur input with the raft sounds nice, but i think its more for backyard-growing for ur own consumption. I plan to grow comercial, means in hundreds or thousands..but first getting experience nd experimenting..

The temperature will be a problem..i read of some heat resistance varieties, nd also the nutrient mix seems to be the key for growing lettuce under high temperatures. i read that a higher nitrogen part in the mix can solve the problem of the high temperature..nd maybe 50% shadow for the plants whhile the hottest hours in the day..what do u think?

check out you tube. I saw a video there of a commercial lettuce greenhouse and they only used rafts.

pretty impressive this video. i will just try all the different systems to find out whats best for the conditions here in my place..nd what has the lowest cost to run it..

"but i think its more for backyard-growing for ur own consumption. I plan to grow comercial, means in hundreds or thousands"

As far as I know, the raft system and NFT are really the only 2 viable options of growing lettuce on a large scale.

yes, after research nd research nd research( Hydroponics makes me realy addicted, i dream already of it hehehe) i found out that the raft system is realy the way to do it. The biggest plus is that no electricity is needed. In my place here we have sometimes Electricity Blackouts daily for several hours..so NFT is not realy good cause i need backup equipment like Generator or something to run the pump..in general, i think the raft system is the easiest and cheapest way to grow lettuce..

Thanks for all ur posts..i will let u know when my first system is running..

Best regards Tom

I think it would be a good idea to aerate the water in a raft system, so I don't know if I would rule out a need for electricity. Particularly on a large scale. I'm sure there are ways around using electricity, but I don't know them. You could use solar or wind to power aerating devices to avoid unreliable grid problems. I've seen them sold for personal ponds. Not cheap, but surely you can find an affordable method for a commercial set-up.