Floating hydro 4x8 ft

PS: I posted this in the DWC section, no one seem to respond. I thought I'd try here. I really want some help with it. Sorry if I've broken any rules!

The following images are showing a big floating garden which is used for lettuces. There is a video on how to build it.


It's about 20 minutes. Pretty interesting, very simple! For those of you who don't want to watch it below is the gist of it.
Take a look! It looks really nice and simple to me.


My question is - Can I make one for myself and use it for you know what ;P? The thing is that I wanna do SOG, so I am thinking for this space 128 plant (4 psf). What do you say people. Can I pull it off?

Yes you can make one for yourself to grow mj but that setup is a bad choice for cannabis. That setup is commonly known as a lettuce raft. Lettuce has a much smaller root ball than cannabis and the growth cycle of lettuce is much faster. That configuration most likely too shallow for cannabis. Cannabis roots are more susceptible to heat related issues (which really equates to oxygen levels) and a better setup for cannabis is deeper but narrower. The wide shallow reservoir is not not such a great idea for cannabis for several reasons. Primarily shallower water keeps a higher temperature than deeper water.

Cannabis root mass can get very large and thus require a deeper reservoir. Also take aeration into account, with a wide table like that you would need many aeration outlets to cover the area where you can use only one in narrower, deeper reservoir.

I would investigate DIY DWC on youtube or even flood and drain (ebb and flow). One of those configurations would better suit a cannabis grow.

FrostyPelican said:

Yes you can make one for yourself to grow mj but that setup is a bad choice for cannabis. That setup is commonly known as a lettuce raft. Lettuce has a much smaller root ball than cannabis and the growth cycle of lettuce is much faster. That configuration most likely too shallow for cannabis. Cannabis roots are more susceptible to heat related issues (which really equates to oxygen levels) and a better setup for cannabis is deeper but narrower. The wide shallow reservoir is not not such a great idea for cannabis for several reasons. Primarily shallower water keeps a higher temperature than deeper water.

Cannabis root mass can get very large and thus require a deeper reservoir. Also take aeration into account, with a wide table like that you would need many aeration outlets to cover the area where you can use only one in narrower, deeper reservoir.

I would investigate DIY DWC on youtube or even flood and drain (ebb and flow). One of those configurations would better suit a cannabis grow.

Click to expand...

Thank you for the answer.

I have considered the aeration, made the calculations will need ~1000GPH for it It'll do. But also I plan to raise a lot of smaller plants (128 pcs - SOG - 4 plants per square foot)With little time for veg. so probably root balls will not be that big. and thought that maybe i wont need that deep. water to manage for the time for flowering

bmdiyh said:

Thank you for the answer.

I have considered the aeration, made the calculations will need ~1000GPH for it It'll do. But also I plan to raise a lot of smaller plants (128 pcs - SOG - 4 plants per square foot)With little time for veg. so probably root balls will not be that big. and thought that maybe i wont need that deep. water to manage for the time for flowering

Click to expand...

Would probably work like that then. With the aeration you mentioned and smaller plants you might be good to go. It's always fun to experiment anyway. Give it a go, why not.

I've tried something very similar indoor 4x4. For about 2 weeks... The main downside is that the raft floats on the surface of the water, leaving no room for air, while most aeration is from the surface. Even tried a venturi on top of lots of air stones.

Hey S~~~ Glad to see you've surfaced.

If that's the video I saw from university of Florida ----- what about high temps outside?

In another thread I chatted with someone growing veggies outside like that-----anyway-----He / she said " of all the plants grown that way required oxygenation".

Higher temps = lower oxygen.

A~~~

Sativied said:

I've tried something very similar indoor 4x4. For about 2 weeks... The main downside is that the raft floats on the surface of the water, leaving no room for air, while most aeration is from the surface. Even tried a venturi on top of lots of air stones.

Click to expand...

I am thinking of suspending the raft, so it could stay at one level, and I'll only fill up the water so it stays a bit bellow the raft. I think I'll get plenty of aeration like that. yeah?

I would wait for Sativied, for that. I think as long as your temperatures are within reason you should have success in almost any system.

bmdiyh said:

I am thinking of suspending the raft, so it could stay at one level, and I'll only fill up the water so it stays a bit bellow the raft. I think I'll get plenty of aeration like that. yeah?

Click to expand...

By suspending it it no longer is a raft and the function of the styrofoam (which on a side note is 'not' light proof) is lost. It's also loses its strength, i.e. when not floating it breaks very easily, especially a large piece with holes in it for the plants can bare hold weight unless it's supported in many places. So in that case it would be better to use something more sturdy (like HDPE plate) essentially making it a simple SWC or even DWC setup.

Something that might work is using a separate reservoir and recirculate the contents of the raft setup. Like a brain bucket in rdwc but with a focus on aeration, perhaps even filter (bio filter...).

What it comes down to is that passive AND mediumless is very tricky, and air stones are not that effective in shallow water.

This is from a large lettuce breeder in NL:


Lettuce transpires a lot of water and grows very fast, but many tests have shown there are numerous craps that thrive in hydro.

Here's a pic from a setup that was specifically created by the university of Wageningen to test the water quality in such a hydro setup.


Some of the conclusions of that research:
- Higher temps result in faster grow but increase chances of getting weak crops
- Continuous aeration results in high O2 (DO level) but can also cause decrease grow rate
- By not circulating the O2 level can drop to 1ppm
- Phytophthora (causes root rot...) was detected in the roots (after adding it on purpose to the water) but did not result in sick plants. (Bacillus subtilis was used with varying results).

For someone with a roof, or garden close to a basement it could be a great way to take outdoor growing to the next level. Put the rez inside, pump it into the water bed (?) and let it drain back.