ok, you have plants in rockwool sitting in a tray which is flooded. the roots will go out of the rockwook into the tray to get nutrients.
so does the tray itself need to have grow medium in it? or can the roots just flop free in there? if the latter then isnt there danger of them drying up?

also, does the rockwool need to be totally submerged in the flooding fluid? or can the flood just touch the bottom of the rockwool and it will wick up into it?

Rockwool Prep:

In this application, running tight spaced cubes with the intention of doing a spike type, mostly single cola grow, 218 cubes are placed into the table. Thats a full table, less 2 for the fill/drain holes. The tray is first flooded to the top of the cubes, with water at PH 4.7 and allowed to stand for 12 hours. This helps keep them from drifting up in PH. They are then flooded with straight tap water to rid of any debris that may have come in the manufacturing or handling of them. Next they are flooded with PH 5.7 water, at this time the cubes should be at PH 6 and ready to accept clones. This is also a great time to check that your table is level.



Each table is a standard 4'x 8' ebb & flow with 2 x 1000wt HPS air cooled lights. Air stones are added to the table and large four inch rockwool cubes are the medium. The cubes are covered with mylar and "X" cuts into the holes that accept the 1" rockwool cubes. This is done to help keep the roots dark, keep the algae growth down and to reflect a light back up to the plants when they are small. I use a very small submersible pump for pumping the water to the table, a couple of shut off valves are also helpful to control the flow and also keep the water in the table for PH adjusting the cubes. A digital timer is used here so that the flood time can be adjusted to the minute.



Above dual picture, shows prepared table with pre-vegged six inch clones inserted and ready to go. Tables are flooded one hour after lights on and again every two hours after that for a total of six feedings during lights on, nothing is used at night. Flood height is adjusted to roughly three fourths of the cube height, and takes just over six minutes to fill, pump runs for eight minutes.

Yes, those small square planters are very restrictive as far as giving adequate room for rootmass. They are really only productive if you are growing from small clones, otherwise they tend to stunt growth and thus reduce potential yield.

Modifying them to have more holes around the sides near the bottom is a must, it will encourage a nice healthy root mat in the tray around the planters.




Building a cover plate to suspend the square planters over the tray will allow the roots to freely flow out of the planters without any possible damage caused by the weight of the planters sitting on the root-mat and blocking the holes. (similar to picture below)



Better yet, use orchid pots or net pots, suspended over the tray by a cover plate with holes cut to place the pots thru.

The suspended planter or *orchid pot method provides the maximum for root mat development. The optimum root mat develops when a modified orchid pot co net pot is used.


Modified (left) and standard (right) Orchid pot co netpots
*Orchid pots are heavy duty net pots made by the Orchid pot company, they are better than ordinary net pots because they have a flange molded into the top of the pot, allowing for the net pot to be suspended in a hole without the risk of the combined plant/pot/rocks weight causing it to fall thru the hole. Orchid pots are available from grow stores and they usually sell for about $1.50 each (10 for $15.00), good cheap and easy to use.

The modified net pot allows for superior root growth and prevents common root damage which can happen when the roots hang down over the sharp edges of the plastic net pot openings.

Another option is to simply fill the entire tray with grow rocks and forget about using any pots or planters, this will give an adequate root growth space. *Almost as good as the suspended orchid pot method.

Hope one of these helps ya out.

So the roots that exit the pots will just hang free in the tray? what about between floods? can't the roots have risk of drying out?

BTW awesome stuff there, but it didnt quite answer my confusion.

Well, in a ebb&flo system, you're going to flood something, we'll call it a bed. In it will be plants in some kind of medium. You can have the bed completely full of medium, and therefore require less solution to flood it, with the plants sitting in the medium. Or you can have the plants in their own separate medium (pots or cubes) and therefore require more solution to flood, but you have the ability to move the plants. The roots will grow out of the cube or pot, and if allowed to dry out, will die off, or "air-prune" as it's called. You want to keep light off the roots, and if roots are exposed to air, you can flood more often to keep them moist.

HTH

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Hey, thanks for the responses. maybe it's the precise scientific type of thought process i have- but let me just ask a few more questions from that....
1) let's say you have pots in the tray. and the roots grow way out of the tray. then there's NO advantage to the roots to have grow medium in the tray itself? so if that's true then basically the only advantage is that it occupies volume and so you can flood the tray higher with less medium?

2) then maybe rather than have messy medium in the tray, maybe some large rocks are better and cheaper?

Just another bit of info on how the guys I know that use ebb and flow tables.they like to make about 4 rows per table.What they do is use rock wool slabs they make 4 rows the lengeth of the table (dont run them over the drain or fill lines.They then like to make holes in each slab for about 10 plants per row so about 40 plants they take thier clones that were grown in 3 inch rock wool cubes and well rooted place the cubes in the openings they made in the slabs.They then fill the table with clay gordan pebbles which hold everything down and give roots good room to hold and spread.Then they use a white plasticon the table like he said he does with the mylar to help reflect the light up.Then its basically follow the flood and drian times and your good.They trim back smaller lower branches which help bigger production and run 1 co2 generator per table with regualtors and guages.They usually get around anywhere from 8-12 oz per plant .You ll have to use netting to help support the big colas or a pvc grid around each one..Lotta bud and you will need massive odor control.I believe they used 3 400 watt switchable digital ballast on light rails..Have fun how ever you go You have a couple of ways now..

Ah, yes, I love filthy fish stories.

To answer your questions, you will probably have roots growing out of the bottom. Don't worry about them, because that means that the pot is completely filled throughout with roots, and they will support the plant.

When using pots, you can fill up the space between them with big rocks, bricks, or what I use is plastic containers filled with water. That just acts as a spacer so less solution is needed to fill.

HTH

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is there any advantage to putting fill between pots, other than to hold pots in place? does it help the roots for them to permeate into some medium versus growing in a matt on the bottom?

8-12 oz per plant?? how big are the plants?

also what is the size of the tray?