The Membrane Meniscus System

Hey everyone, after reading about the membrane meniscus hydroponic system on Larry3215's thread:
https://www.rollitup.org/t/three-types-of-hydro-in-a-small-tent-on-one-airpump.960095/
I did a little digging, got in touch with the inventor Andrew Parker and also read his book on the system.

On paper it seemed like the next step in hydroponic systems as it claimed to be a recirculating system where the PH and EC dont change throughout the grow, the roots get the maximum amount of dissolved oxygen and it doesn't even require any electricity.

In a nutshell, this system works as a sort of hybrid NFT & wick system, the nutrient solution flows very slowly from one end of a flood tray and drains on the other, while on top of the flowing solution sits a second thin plastic tray with a bunch of holes in the bottom that are protruding slightly upwards to discourage water from flowing back down, this second tray is just touching the solution, not submerged in it, on top of this tray comes the membrane which is a tightly woven thin nylon fabric, this fabric is there to keep roots from growing down into the solution while still allow them to wick water up from the bottom, thus creating a constant upward movement of solution, never down, essentially keeping the solution flowing beneath in pristine condition.

since the roots are always in contact with the wet fabric, due to capillary action they are coated with a thin meniscus film of nutrient solution and in that thin film is where the dissolved oxygen is highest.

So i decided to go ahead and test it out, i built one according to the instructions in Andrews book and since i only have room to test this outdoors i decided to grow micro dwarf tomatoes, they stay very small and compact while still producing flowers and tomatoes and therefore have a higher nutrient demand then say lettuce..

This is what the system looks like:

on the left is a 30L barrel that contains the solution, its connected with some black tubing and a valve to the bottom left side of the tray, the solution flows on the bottom of the tray and drains out the other end into a 20L collection bucket at a very slow rate, around 1 drop every 3-4 seconds, the bucket is manually dumped back into the barrel every week or so when it fills up.

this is what the root zone looks like, what you see here is first the nylon fabric which sits on top of the plastic diy tray, you can see where the holes in the tray are thanks to the fabric that is being pushed up a bit.

Since i started this a few weeks ago you get to see the progress without waiting
This is 9 days ago:


This is 5 days ago:


since starting this grow the EC of my solution has not moved, PH been holding steady at 6.7, im using tap water and masterblend 4-18-38 + calcium nitrate + epsom salt as fertilizer.

So far so good, i'll take more pictures tomorrow.

Wow thats super interesting

Awesome! Glad you started this.

Your roots look super good so far.

Why the PH at 6.8? Is that what the tomatoes like or did Andrew recommend that hi a PH?

Toms prefer 5.8 - 5.9

6.4-6.7 ph is the range for this fertilizer combo as far as i know..thats what i've always used for tomatoes,
Andrew didnt recommend any specific fertilizer or ph range, but i think it makes sense to avoid using organic fertilizers in this system.

I would check which iron (Fe) chelate masterblend uses, EDTA will struggle at ph 6.4-6.7, if its DTPA its not so bad. Dwarf toms are ideal for limited space, the only downside is the toms all arrive at once I have 45 growing in an outdoor vertical hpa setup.

those are some nice looking dwarf tomatos, im looking at a bunch of small ones in a barrel configuration right?, which variety are they? i've grown dwarfs before but regular dwarfs can still get big, just takes much longer, i needed an even smaller variety so i ordered a bunch of micro dwarf tomatoes, they stay tiny, only produce cherry tomatoes, perfect for testing in small spaces.

having a hard time finding which chelation agent is used by masterblend... might have to shoot them an email.

EDIT: my PH meter wasn't calibrated apparently, just calibrated it and retested the nutrient solution, its actually at 6.3..i guess that makes more sense.

The toms variety is called minibel, they reckon to get a foot tall but i`ve grown them before and its not always the case. The barrels are repurposed water butts around 60 us gal each. PH 6.3 is about as high as i`d want to go but you`ll be ok at that

Houston we have a problem!
took a new root pic today and found this sneaky root on the left side wall growing underneath the nylon fabric


the first layer of containment was breached! its only a matter of time now until the roots make their way down the tray holes or sides to the bottom... the only way i'll know when is if the PH/EC starts to move, im gonna have to find a tighter weaved fabric next time...

Yeah, that looks pretty loosly woven now that I can see the pattern. The fabric I was using had a much tighter weave. You cannot see individual threads in the stuff I was using. Im pretty sure the fabric I have is rip-stop. There are no loose fuzzy threads at the edges like yours. It doesnt unravel at all.

The roots also got through my fabric but they found a hole or a rub spot. It was at a corner where I pulled it tight over the frame that held it in shape, so I may have caused it by rough handling.

It might not be too late to make a change now unless the roots are too firmly bonded in the fabric. My roots pealed off pretty easily. If your peal off you might be able to save them.

here are a couple of closeups of the fabric I had.

He also mentioned using shower curtain fabric.

i have a real problem getting my hands on some real ripstop, god knows i've looked around, i have some tightly weaved polyester fabric im thinking of using, not sure how well it will perform as a membrane though... since the roots dont appear to be sticking to the current fabric and the breach is only on that one side i might be able to lift everything up and switch out the fabrics...

On the other hand, this wont kill the plants - it just means you are not going to be able to rate the effectiveness of the meniscus system.

You can get it from Amazon:

https://www.amazon.com/s/ref=nb_sb_ss_i_3_7?url=search-alias=aps&field-keywords=ripstop+nylon+fabric&sprefix=ripstop,aps,249&crid=3PT412Q89LEI8

The downside to that is you cant look at it before you buy it. Not all ripstop is the same and thread count/tightness of the weave will matter.

The shower curtain I have in one of my baths looks to me like it would work, but my wife likes the color so you cant have it

Someone somewhere talked about using silk screen fabric to successfully stop roots, but they couldnt remember what mesh they used. In my test, the silk screen I used let the roots through, but I chose a fabric that was a 140 mesh (55T) fabric. There are much smaller mesh sizes. I dont know what the smallest mesh size is, but you can get up to at least 300 mesh, which should (might) be small enough.

Very interesting

subbed

Welp i decided to change out the membrane for the polyester fabric i had as a backup and let me tell you, it was an absolute pain in the ass, had to give the roots some pruning as there was no conceivable way to get them situated on the new fabric properly with the amount of roots that they had..

not sure why some roots appear white and some brown in this picture, they all actually look pearly white.


What a mess.


Roots under the membrane but did not escape the sub layer tray.


Cleaned the roots off, this is what the sub layer tray looks like.

New fabric, not my best work, had to hurry so the dangling roots wont dry out.


This pruning session will probably send them into some shock, but i have no doubt they will recover.. hopefully this new fabric holds up better..

Well done! My fingers are crossed for you!

Thanks man.

Update time, the plants didnt seem to mind my pruning session, this is yesterday:


and this is today:

on the topside the plants look great and im seeing tomatoes starting to form:


my nutrient tank is almost empty and not once did i have to play around with the PH or EC, i didnt have to change out the water and i didnt use any peroxide, as long as this new fabric holds the roots in we gucci , i might add a tiny pump that would replace me manually dumping the excess back into the main tank, then i really wouldn't have to do anything, i dont see myself growing hydroponically any other way, this is just maintenance free..

Very nice!

Have you grown this type of tomato before? Can you tell if they are developing any faster or better than with other grow methodes?