Media-less ebb n flow

Hey Skiball, I used to do DWC and then switched to Medium-less Ebb and Flow (I mean no hydroton whatsoever, the roots are hanging mid air).

I made this setup only because I didn’t want to deal with any media. Here’s a schematic of my setup

So my setup worked by turning the pump ON for about 2 minutes (in my case for the tank sizes I had) and this will completely empty the tank inside the tent to the nutes tank outside the tent, then turning the pump OFF for about 10 minutes and the water will slowly flow back to the tank inside the tent through the now-turned-off pump and so on and so fourth indefinitely.

Pros:
1- The nutes tank is outside the tent which made the water temperature much cooler than when I was using DWC.

2- I believe this setup helped me further avoid any root-rot problems. I can’t make a clear statement on this as I was using Benes (Great White) which got rid of my root-rot even when I was using DWC. But all in all, I believe the temporarily exposed roots should help reduce the root-rot problem anyway.

3- I could very easily access the nutes tank to measure EC and PH or to add water and nutes without disturbing the plant or even opening the tent.

4- Specific to my Ebb and Flow setup, if the electricity goes out for any reason or the pump malfunctions, the pump will shut down and the water would naturally flow back to the tank inside the tent, saving the plant from dehydration.

5- I didn’t use an air bubbler nor an air pump. The pump I got had a Venturi which I connected to an air hose and it would make bubbles on its own. Note that the air inlet should be above water level at all times.

Now for the Cons:
1- It’s a little more involved setup as I had to get a timer for the pump On-Off cycle but that’s not a big deal really!

2- Not using a hydroton made me run the pump cycle much much more frequently (2 Munites ON, 10 Minutes OFF) compared to a normal Ebb and Flow where the pump might run only twice a day.

Lastly:
I didn’t notice any difference in grow times or yield from the DWC, actually I might have noticed that this setup made my plants grow healthier but I didn’t do a side by side comparison.

10 Likes

Thats a very simple, effective setup. I like it :slight_smile:

2 Likes

@Mohamed
How do you prevent the tank in your tent from overflowing?
Because by the law of the communicating vessels, the water will continue to flow from the tank outside your tent tot the tank inside your tent until the levels of the tank outside the tent and the tank inside the tent are equal.
Curious what you came up with.

1 Like

The tank probably isn’t as big as what’s pictured in the diagram bud.

Still.
It does not matter if it is big or small.
The levels will even out when the tanks are connected with a tube.
I wonder how he fixed it in such a way that the level in the tank inside is always to the correct height.

You can see in the diagram the pot is elevated. How would water defy gravity?

If the pot (I guess you mean the reservoir outside) is elevated, the water will indeed flow from the reservoir to the tank inside (the tray). But physics tells us that the water will keep on flowing until the level in the reservoir and the tray is on the same height.
That is the law of communicating vessels.
If the reservoir is very full, the tray will overflow. If the reservoir is nearly empty, the water in the tray will not reach the desired level.
If this system wants to work, you do want to have something that ensures that the level in the tray will always be on the same and desired level.
I am curious what this solution is.

1 Like

Sorry for the late reply RobRoy, you’re completely correct but only in case I fill the outside tank fully. The tank is made purposefully bigger just to hold the extra water gushing in when the pump is on.

In other words I do the following:
1- with the system empty of water, I start filling the outside nutes tank with water until the water in the “tent” tank at about 3/4 full. This way I ensure if anything malfunctions, the water will cover the plant roots.

2- when the pump turns on, it starts pumping water from inside to outside. The outside tank still have enough head room to contain the water coming in until the inside tank is empty. At this point the pump will stop working because it’s sucking air, so I set the timer to stop the pump right before it get to this situation, mainly to elongate the pump life and avoid the nasty noise coming from a pump sucking air.

So you see the tank in the photo is actually the correct size but it wasn’t intended to be completely filled with water.

3 Likes

I’ve actually been noodling over media-less ebb and flow, and the more I think about it the more it starts to look like DWC.

But, I’m still experimenting. I too am tired of dealing with hydroton, and I managed to get rid of all media in my DWC grows, but I’m trying a “low media” approach to E&F.

I’m running a bunch of seedlings in hydroton only, no rockwool, in 4" netcups, and all netcups are resting on a 1" coir mat at the bottom of my flood tray. My thought process being that the roots of the seedlings will go down the hydroton and spread into the coir mat.

I’m flooding 1/hr, for about 2-3 mins at a time, and I’m currently running 0.3 EC on the seedlings and will be running 0.6 EC once they get their root systems large enough.

This is my first ever E&F and so far I haven’t killed anything!

3 Likes

All the different types of hydro/aero can be looked at or compared as different levels of aeration or different mixes of water time vrs air time.

One thing you need to know is that oxygen is relatively slow to dissolve in water. The very very very thin surface layer of a bucket of water will quickly reach 100%DO, but the lower portions of the water will not increase in O2 for some time. The O2 is slow to migrate through water from the surface contact area.

At one end is DWC and all its variations. The majority of the roots stay submerged 100% of the time. They depend entirely on the dissolved oxygen in the water. This is why DWC needs constant aeration in the form of air stones, flumes, water falls, etc. You need that to insure that all the water deep in the bucket has the same O2 levels.

The next level up is Ebb/flow. Well, depending on how long you flood. When you flood the roots - with or without medium - you are submerging the roots in deep water. During the flood, the roots can only get O2 from the water - just like DWC. So you also need to aerate the water in the rez.

However, during the drain cycle, the roots will be left with a very thin layer of water coating them - the meniscus layer. That very thin layer of water will absorb O2 from the air relatively fast and can transfer it to the roots much faster than any thick layer of water. That means the roots get an O2 boost during the drain cycle. Longer drain cycles than flood cycles are to be preferred as long as the roots do not actually dry out.

Thats where a medium can be useful. Things like hydroton, rock wool etc hold more water than the roots by themselves. Plus they hold it in such a way that the roots can only get to a very thin layer of it at any given time. That means the roots can stay wet with that very thin meniscus layer for a longer time. This ends up giving them better O2 absorption.

The downside to that medium is its a heck of a lot of trouble. I see no issues with going mediumless as long as you carefully time the drain cycle so the roots do not dry out. Its a somewhat trickier/riskier balancing act with no medium, but a lot less trouble.

The next step up would be things like LPA followed by NFT (if done correctly). LPA floods the roots during the ON cycle, but leaves them in open air slightly better than with flood/drain - but not by much. Most folks are afraid to let the roots dry out and use way too long an ON cycle. You just need to get the roots covered in a layer of water, then let them dry out. Leaving the sprayers on for minutes at a time is defeating the whole purpose and just lowers the O2 transfer efficiency.

The key to best results with all these types of hydro is balancing the wet/dry cycles. There is no “best” number. You just have to let the roots sit with that super thin layer as long as possible - without drying out completely!

NFT has a lot of potential as far as O2 transfer because its supposed to provide that THIN FILM of water. Unfortunately, almost every one over does it here too, and really floods the roots. True NFT provides a “film” of water not a flood of water. If you are flooding the roots, you may as well to dwc.

The next step up would be more exotic types like Membrane Meniscus. This is really the ultimate in NFT. It keeps the roots with the thinnest possible meniscus layer 100% of the time with zero flooding. It can produce some really great results, but is very difficult to do in practice.

After that we get to HPA and AA aero techniques. Both of which keep the roots growing in air 100% of the time with just micron sized droplets floating around. In theory, the roots are never flooded. Done correctly, this is the ultimate as far as aeration levels. The problem is both are more technically demanding as far as hardware, plumbing etc than other hydro types. They also require a lot of finicky timing and fiddling and trial and error. if you over do it with the mist, you end up with roots no better than LPA. If you under do it even a little, you dry out the roots, and that is bad :slight_smile:

Many people claim that various different techniques work better than others. I personally find that HPA and AA do produce higher yields - as long as you dont screw it up! However, Im not really convinced the increase is all that much. Maybe 10%-20% over other types of hydro at the most. I think most folks who go for HPA/AA are really into it because they like to tinker with gadgets and gizmos more than for the extra yields etc. I do it for that reason and because Im addicted to fuzzy roots! Any extra yields - if they occur - are just a nice extra. :slight_smile:

2 Likes

So this means that when you fill up the outside tank the level in the tent tank is 3/4.
But after a few days, some of the water has been used by the plants. Thus there will be less water in the system, and therefore the level in in the tent tank will not be up to 3/4 anymore, but only to 2/4 or 1/4.
How do you prevent that?

Float valve would do it or refill by hand every few days.
Having a massive res also helps, would take longer.
Such a clever system.

A float valve in the outside tank could work, but I don’t see that in the drawing. Besides, then you need two outside tanks.

A massive outside tank would make no difference at all. It has to do with the law of communicating vessels. Only if it would be an outside tank that was really wide instead of high.

I don’t see the cleverness of the system yet (compared to traditional E&F for instance)
With normal E&F the level of the water in the tent tank is always the same. This will be great for the roots. You also don’t need to refill your outside tank every day.
Mohamed also states that in case the pump will fail, the water will flow to tent tank and thus prevent dehydration. But roots can survive longer without water then plants can survive without oxygen. So that is another downside to this system imo.

2 Likes

Yes either a connection to tap or top up res.
I would do refill by hand if I was operating this type of system like I do now. I use regular DWC because it reduces complications of construction and management in my limited space. I want to avoid all possible leak risks and save space so I will not go to that kind of setup. Still I appreciate the pump out concept as a solution, it is something I had not thought of before.

As far as I understand, submerged roots will manage for maybe 12h if not longer, kratky method is often used for vegetable crops for months on end and that is standing water. This leads me to believe drought will kill the plant faster.
If you have some other criteria or examples I welcome that gladly.

If you have limited space, then traditional E&F with the tank underneath your trays is also a good option. If something leaks, it will leak in the tank.
A pump outside is not always a good thing. Leaks happen mostly where there are connections. Also a pump that runs dry and is not surrounded by water can overheat.

In Kraktky the concept is not that the roots are in water 24/7. The basics of Kratky is that when the plant starts drinking the water, the water level will go down. So the gap of air will get bigger and bigger as the plants grow.
Vegetables like lettuce and herbs (fast growing leafy crops) will grow well in Kratky. Cannabis (fruit bearing) will do not so well.

3 Likes

I really love the piece you wrote. Very clear and explaining well all the aspects of hydro.
There is just 1 thing I do not agree with you :slight_smile:
And that is in the quote above about E&F.
When you start pumping water into the tray, the water will be moving. During this moving the water absorbs O2. Also when the pump stays on there is constant movement of the water. All this time there is plenty of O2 in the water. So there is no need to extra aerate water in a rez in a E&F system.
Maximum DO is reached in such short time, as long as the water is moving one way or the other.

What I also liked in your text is the word meniscus layer. Never heard of that word, but English is not my language. But the way I understand it (when googling it), the meniscus layer is more about the shape of a liquid that is in contact with another material.

The biggest problem with media-less ebb and flow is that it’s very inefficient… Unless you’re doing it this way
unnamed

You’ll need some of these for a better bottle to PVC connection (better adaptors vs the ones used on the picture above)
Bottle, O-ring, Bushing, and PVC pipe

In what way is it inefficient?

Usually in a typical ebb and flow system medium is used (mostly Clay pebbles) to fill in a tray/bucket, which in turn means less space for the nutrient solution to fill.

Empty space = more nutrient solution to fill the void.
More nutrient solution = more money for nutrients & water.

1 Like

yes, in that way it can be a bit inefficient.
On the other hand: you need less stuff to buy, less stuff to clean. In that way it is efficient.
You can also perhaps fill the tray to a certain height For example 2 inch instead of 4 inch.
The system with the bucket gives roots less space to grow. That could also be inefficient. Not sure.
Would be nice to do some side by side tests.

2 Likes