First Ebb & Flow

[Keesje]

Was flooding every 3 hrs day (4 times) and once mid night for 15 min per (with air stones under each pot) in hydroton; changed it to 10 min every 2 hrs with no flood during the night and they are loving it. Interested to learn if more people flood more often than that.

How did you put an air stone in an ebb&flow system?

 

[zypheruk]

The quicker your roots fill the pots of hydroton the more waterings they will need, more waterings = faster growth and better yield. The roots are not searching for nutrient and water this way.

 

[Keesje]

A cubic meter of air holds about 1,400,000 mg of O2.

I was incorrect here.
A cubic meter of O2 weighs about 1.400.000 mg.
Air consists for about a fifth out of O2.

 

[Renfro]

How did you put an air stone in an ebb&flow system?

Probably chucked it in the reservoir, you know to destabilize the pH lol. Pointless to use an air stone with flood and drain.

 

[Keesje]

"why' would have been my 2nd question

But you are right indeed: Totally useless to have an airstone in another hydro-system like waterfall, ebb & flow, drain to waste.
The movement of the water is the reason that the water absorbs oxygen.
(The same with an airstone btw: It are not the tiny bubbles that bring the oxygen in the water. It is the movement of the surface once the bubbles get there)

 

[Mechanicalbuds]

'Old air' does not exist in reality.
We sometimes talk about 'old air' in a room, where we ask people to open the window to get in some fresh air.
But that has nothing to do with lack of oxygen. It has to do with the fact that the amount of CO2 gets above a certain point.
It makes us feel not well, tired.

Using up all the oxygen could only happen in a 100% sealed box or something like that.
In hydroton however there are gaps where air can slip through. So fresh O2 will always slip through the gaps once the roots absorbed it.
So the air can not get old > The O2 can not get used up. It is a physical impossibility.
It is like 'communicating vessels'. Gasses will get evened out. (perhaps I am using the wrong words)
Imagine having two sealed rooms and in room A a candle will use up some O2.
The moment there is a small opening between room A and room B O2 will stream from room B to room A to even out the amount of O2.
The moment you open a window in either of these rooms, the amount of O2 will be at the same level in room A and B and outdoors.
The same with hydroton: The amount of O2 will be the same in between the pebbles and outside of the netpot.
O2 that is absorbed by the roots, will be filled up by new O2 in a second.

Of course in extreme circumstances, O2 can not move fast enough. But then we are talking about the the bombing of Dresden or something like that.
But we are talking about roots that use about 200 mg of O2 per kilo of roots per hour.
A cubic meter of air holds about 1,400,000 mg of O2.


I am saying nowhere that hydroton doesn't need to be flooded often (or less often)
Getting in water+nutrients is a very good reason to flood. In my opinion more times flooding is also better. (based on some tests that I saw, and my thought that in that way the roots have more opportunities to 'drink'.)
So for reasons of getting in water+nutrients.
Not fresh air/O2. For that reason it is useless.

A deep vessel filled with rock gets no airflow at the bottom. When the 02 is used it can't be replaced until it is pushed out from the bottom. It does not matter what you call it. When flooding happens it brings new air with oxygen to the roots. You say that does not matter, I find otherwise.

Roots need to stay moist but the also need oxygen. When they use up the oxygen it needs replaced. Hints the term "used or old" air. That's why ebb and flow is better than most other forms of hydro, ino.

I'm not trying to argue, I feel you are hung up on a phrase confusing what was actually ment.

 

[Keesje]

We are not arguing.
We are talking about how we both think that things work.

I have some questions:

A deep vessel filled with rock gets no airflow at the bottom. When the 02 is used it can't be replaced until it is pushed out from the bottom.

How come it can't be replaced?
And if the O2 is used up, there must be some kind of vacuum there now, if new air can not come in?
Are the rocks so small that there are not even gaps of 2 mm, 1 mm or 0.5 mm?
If air can not reach those spots, how come water can get there?

I am really curious about your answers.
Because if what you say is true, how do roots in soil ever get oxygen?
Soil is far more dense then hydroton. The particles of soil are way smaller then any pebble of Hydroton.
So it is all packed together and still oxygen gets to the bottom of the pot. Even if it would be a pot of 20 gallons... oxygen will still reach the roots at the bottom. Except when you over-water of course.

 

[Mechanicalbuds]

Cool. Not arguing.
Your right, there is gaps in rock.

I don't think if the 02 is removed there will be any sort of vacuum to pull more 02 in.

My table had 1 gallon nursery pots for holding rock. When filled, and watered, and then let to sit for several weeks( like when I'm lazy and dont clean after harvest....) The bottoms are always still wet. Its about airflow. There is no breeze getting air in there. If air was moving at all it would be dry like the top 3 inches of rock. The top will always dry quicker right? Because is can escape easily. But the bottom, no. Its trapped.

There is gaps as you say, yes, but no air movement....

Does that help explain some?

Ps. I'm no science guy, I struggle like everyone else!

 

[Keesje]

True, there is not really an airflow (the same as in soil)
But that doesn't mean that O2 does not get there.
The molecules are so tiny, they can slip through the smallest gap.
Like in soil. Plants even grow in clay soil (would not suggest it for your grow though )
The benefit of Hydroton is that even more O2 can slip through then in almost any other medium.

That your bottom stays damp has probably more to do with the fact that the water can not evaporate very well there. Some airflow would help, true. But there is still plenty of O2 there. Not of course when the bottom of your pot is closed and there is a layer of water.
O2 will sneak through the smallest and tiniest holes.
Thank God for that, otherwise corpses in a graveyard would never decompose

 

[C@nn@b1@n]

I have a airstone under the netpots on the same timer as the pump. Not pointless as only 2 of the pots (of 4) have airstones are they are significantly larger.

 

[Keesje]

I have a airstone under the netpots on the same timer as the pump. Not pointless as only 2 of the pots (of 4) have airstones are they are significantly larger.

So I guess you have buckets or something like that.
In each bucket hangs a netpot.
When the bucket fills up with water, also an airpump with an airstone begins to work.
Something like that?

 

[JohnDee]

How did you put an air stone in an ebb&flow system?

Just wanted to mention...back when I first did hydro, E&F...there was a little fitting that came with my water lift pump. It was a 1/2" fitting with an air connection on the side. Not sure what it was for...I stuck it on the hose going up to the tray. Plugged airline into it...and plugged the air pump into the flood timer. So air got injected into the hose as the water rose up to the tray. Had the parts...why not. Never had any ph issues either.
JD

 

[Keesje]

Just wanted to mention...back when I first did hydro, E&F...there was a little fitting that came with my water lift pump. It was a 1/2" fitting with an air connection on the side. Not sure what it was for...I stuck it on the hose going up to the tray. Plugged airline into it...and plugged the air pump into the flood timer. So air got injected into the hose as the water rose up to the tray. Had the parts...why not. Never had any ph issues either.
JD

Sounds like a venturi

 

[JohnDee]

Sounds like a venturi

Or some kind of snifter port...for anti-siphoning. Anyway...worked good.
JD

 

[Keesje]

Normally E&F must be more then enough to have maximum DO in your water.
So it is pointless to have an airstone or a venturi.
Also, one of the main benefits of E&F is that in 'Ebb' the roots are surrounded by O2 in gaseous state while they are still wet.
Only if the E&F system is not designed well or something else is wrong, airstones or venturis would perhaps give some benefit.
But I don't see which one that could be.

The easiest thing to reach in hydro is maximum DO.
Only in systems where the roots are in water 24/7 it can sometimes happen that the rootball is so dense, that the water inside this rootball does not change enough. Then an airstone underneath this rootball could help.
But with E&F the rootball is relatively dry now and then. So there is always enough O2.

 

[PopeyeSpinach]

Was flooding every 3 hrs day (4 times) and once mid night for 15 min per (with air stones under each pot) in hydroton; changed it to 10 min every 2 hrs with no flood during the night and they are loving it. Interested to learn if more people flood more often than that.

Well I can tell you that having air stones in a reservoir for Ebb and flow makes th PH spike more. If you have them in the tray, Ive never done that. And it sounds kind of weird too

 

[C@nn@b1@n]

Well I can tell you that having air stones in a reservoir for Ebb and flow makes th PH spike more. If you have them in the tray, Ive never done that. And it sounds kind of weird too

I've run buckets with airstones for years, so when switching over to ebb and flow (initially I was running 4 on/off @ 15 min) I felt running it that long without air would drown them. I left it in (switched to 8 on/off @10 min) and the 2 that don't get air are nowhere near the same size.. The next run will have even more air than this one.

 

[Keesje]

I've run buckets with airstones for years, so when switching over to ebb and flow (initially I was running 4 on/off @ 15 min) I felt running it that long without air would drown them. I left it in (switched to 8 on/off @10 min) and the 2 that don't get air are nowhere near the same size.. The next run will have even more air than this one.

I don't really get your ebb & flow schedule.

 

[PopeyeSpinach]

I think your flooding way to long, you should never need airstones and they should not make a difference. I dont think ive ever flooded for more than maybe 4 minutes every 4ish or more hours. Just long enough to flood the tray full and circulate the reservoir solution a bit.

Once a large root mass has grown, it will retain water for a while. Ive had days go by after harvest before i cleaned my flood trays out and they are still wet.

 

[Renfro]

With flood and drain using hydroton I flood just long enough to reach full depth, no longer. I wait 4 hours before flooding again. I do NOT flood when the lights are off.