Why water change day seems to grow aquatic plants better

Tom Barr

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Matt, if it's just clean water, then activated carbon and the plant uptake themselves do that already.

This is a case of us Hobbyists wanting to believe something.

If we think about it more, we can ask the question, what is it that helps?
What helps the plants GROW more/less?

Then what can you conclude?

We do not conclude that nature is best for growth and then see what facts we can find to support that.
Many plants come from ditches, ponds/lakes, backwaters and many are not even found in water in natural systems.

But...water levels do change a lot in nature.
 

Wwh2694

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I do water change every 3 days to fast grow HC and don't see any algae. This is the key is you want to have a nice growth on your plants for IAPLC. ;)
 

Tom Barr

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Wwh2694;105239 said:
I do water change every 3 days to fast grow HC and don't see any algae. This is the key is you want to have a nice growth on your plants for IAPLC. ;)

I agree 110%.

2x a week water changes for good scaping seems to be a good rule of thumb for water changes.

I do this on my 120 Gallon, and it's clear that the tank does much better with more frequent good water changes and cleaning.
Many discus keepers already do this routine, which is where EI sort of came from also.

Still, what causes the plants to grow so well post water change?
It's not just new or clean water.

That alone does not "grow" plants.
 

thinbear

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just thinking out loud here (very messy thought, will read more ref. when I have time):

  • certain changes stimulate/trigger plants to release more plant hormones
    - temperature shock: trigger the release of plant hormone;
    - the graduate raise of temperature make them believe "spring is coming", thus produce more plant hormone, ie promote growth rather than converting sugar for storage;
  • dilution of competitors
    - Removal of algae, thus less competitor fighting for available resources;
    - Removal of certain microorganism that prohibit the growth of plants?
  • Cold water are more likely to enter the plant cells (higher density than warm water), thus facilitate the material uptake? (but warm water have higher energy for diffusion and active transport...)
  • fresh water has lower water potential, thus the guard cell will keep open (which facilitate gas exchange) until they adjust to the new water parameter Nvm, most aquatic plant don't have stomata
 
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Tom Barr

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Hi Thin bear,


You can allocate larger fruit in crops etc, but the total growth of the plant will not change.
Gibbing the grapes etc, or more roots, storage, more flowers etc.
There is one obvious PGR: ethylene
Like CO2, ethylene is a gas. And the flux is 10,000 slower in water than air, some when a plant is flooded,/submersed, or unflooded, emergent again.......the gas will then dissipate.
In the submersed state, the plant's ethylene will accumulate.

Does this affect aquarium plants when we do a water change?
Or like occurs in tidal freshwater systems that get flooded and emergent 2x a day?

Perhaps. There might be something to that.

As far as switching to various storage organs, this is generally not done in 95% of the plants we keep, they are all in vegetative growth mode.
Some pondweeds, Hydrillia, Sago pondweed, some Aponogetons, Nympheaceae etc. We just do not see much asexual propagules and certainly much less seeds/flowers etc.
Still flower production due to water changes has not been noted in aquarium plants. Blyxa aubertii is about the only example/exception I'm aware of, but there was no control either.


the likelihood competition in minimal since the nutrients are fully non limiting for algae. Same for plants(easy to do).
There might be some slight effect due to the boundary layer reducing CO2 or light a small amount perhaps.
Same for the periphyton bacteria and fungi. But nice clean plants would be used as a control anyway in this example.

Few microbes inhibit plant growth, most rely on healthy growth of plants for a supply of O2 in the sediment.
Microbes give off a sticky exocellular matrix when they are actively growing well........this seems to clarify the water.
Many aquatic plants have stomata, but they are non functional typically.

Warmer water would be more likely to enter the plant and speed up processes vs cold water.
Colder water = more O2.

Good points thinbear, the ethylene might have something or an effect. I do not think anyone has looked at it in tidal vs non tidal systems. Ecologically, this would be interesting.
 
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Nanobubbles. These bubbles cannot be out-gassed easily and can remain in water for months with very little out-gassing. They allow live fish to be frozen and defrosted without any signs of harm. They even cure fish herpes. Check out page 25-6 of this PDF which shows the growth of plants with and without nanobubbles. Nanobubbles cause plants to grow faster and allows terrestrial plants, such as orchids, to survive for months partially submersed in water.

http://staff.aist.go.jp/m.taka/nano-bubble.pdf

If this is the reason why plants grow faster with frequent water changes, then there needs to be a way to add water that doesn't contain nano-bubbles. If this water does not cause plants to grow faster, then it is most likely nanobubbles that drive plants to grow faster.
 
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Yo-han

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What about a simple explanation as the lower water level during the water change. This gives more light to the plants -> increasing growth. This can easily be tested by removing the water in the same speed as it goes in.
 

Tom Barr

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Yo-han;106982 said:
What about a simple explanation as the lower water level during the water change. This gives more light to the plants -> increasing growth. This can easily be tested by removing the water in the same speed as it goes in.

Assuming the new tap does NOT have degassing nano bubbles.

The other thing is to simply test a water change without actually exposing plants to air.

I do not think the increase in light is significant to cause the effect from a large water change, water and reflection does not remove that much light and the process is only 30-45 minutes for the majority of aquarium water changes.

Lights can also be turned off during the water change, then turned back on to show this(I've done this to prevent drying out of the plant leaves when exposed to air).
 

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Solcielo lawrencia;106962 said:
Nanobubbles. These bubbles cannot be out-gassed easily and can remain in water for months with very little out-gassing. They allow live fish to be frozen and defrosted without any signs of harm. They even cure fish herpes. Check out page 25-6 of this PDF which shows the growth of plants with and without nanobubbles. Nanobubbles cause plants to grow faster and allows terrestrial plants, such as orchids, to survive for months partially submersed in water.

http://staff.aist.go.jp/m.taka/nano-bubble.pdf

If this is the reason why plants grow faster with frequent water changes, then there needs to be a way to add water that doesn't contain nano-bubbles. If this water does not cause plants to grow faster, then it is most likely nanobubbles that drive plants to grow faster.

Well, they suggest that micro bubbles last several minutes, which is plenty of time. Claims by some hobbyist are saying 5 seconds or less, which is highly suspect IME.
 

Tom Barr

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Observations:

CO2 reactor chamber gas build up and reduction.
1. When I do water changes on a 350 gallon system, as well as a 220 gallon system, as well as my own aquariums, the CO2 runs and has a powerhead that supplies the flow to the reactor.

2. The water from the sump is pumped into the reactor during the water changes.

3. Since no flow from the main tank occurs, the CO2 concentration in the sump water climbs. This causes the gas build up in the CO2 reactor to grow much larger relatively quickly, a few minutes and pretty much exceeds the reactor's ability to catch the larger visible bubbles.

4. This gas build up is rapidly remove once I turn the main pumps back on.

I know/understand water change contain very high ppm of CO2, however, the gas build up inside the reactor presents an issue there. The gas from the CO2 tank is pretty much pure, pure enough not to cause this rapid build up, and if it's so hard to dissolve into solution, why is the gas bubble occurring so fast during the water changes and then dissipating rapidly once the tank water mixes?

If the gas in the chamber is so hard to dissolve, why does it rapidly dissolve into the tank water, but not the sump water?
Why does it build up so fast once the tank water supply is shut off?

CO2 source purity is roughly 99.98% and has to be 99.90% pure legally(beverage grade). Carbon gas prefilter can be added to remove most of the other potential gases. Still, at this tiny 0.1% fraction of gas, it cannot explain the accumulation rates seen in the reactors. If the other gases do not dissolve easily into the tank water, then they should remain once the water from the main tank is reintroduced back into the sump, but that does not occur.

Perhaps the CO2 is saturated rapidly(1500 ppm etc in solution). This seems unlikely, but possible.
It may be as you get up higher in concentration, the ability and efficiency of the CO2 reactor drops considerably.
And then you see a subsequent increase in the gas bubble in the chamber.

At low tank water CO2 ppm's, this dissolves fairly quick, but not at higher levels.
There's not enough other gases in the sump water to cause this effect.

It's pretty much all CO2, which suggest the CO2 does NOT dissolve in a few seconds even at higher concentrations.
A few minutes, but not a few seconds.
The gas seems to be mostly CO2 and at the higher ppm's, it does not dissolve readily compared to lower ppm's.

Next test
: measure CO2 ppm in the sump water and the change in pH as the gas builds and accumulates.
 

Yo-han

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Solcielo lawrencia;106962 said:
Nanobubbles. These bubbles cannot be out-gassed easily and can remain in water for months with very little out-gassing. They allow live fish to be frozen and defrosted without any signs of harm. They even cure fish herpes. Check out page 25-6 of this PDF which shows the growth of plants with and without nanobubbles. Nanobubbles cause plants to grow faster and allows terrestrial plants, such as orchids, to survive for months partially submersed in water.

http://staff.aist.go.jp/m.taka/nano-bubble.pdf

If this is the reason why plants grow faster with frequent water changes, then there needs to be a way to add water that doesn't contain nano-bubbles. If this water does not cause plants to grow faster, then it is most likely nanobubbles that drive plants to grow faster.

Looks promosing on all fronts. Maybe this is what happens with an ADA style diffusor and doesn't happen with a 100% dissolving CO2 reactor. Really curious about the survivability of animals in frozen oxygen nanobubble water as well. Thanks for sharing! Will keep me busy for 10-20 hour I guess:p
 

gsjmia

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Tom, I don't have any scientific knowledge or back round to add or comment on what you said, but I do know that beverage carbonation takes place in the carbonator tank under about 45 lb's of pressure generated by the cabonator pump.

It seems me that water can only absorb so much Co2 at ground level atmospheric pressure and in order to absorb more it must be done under increased pressure. The inverse is true when you pop a soda can and get carbonated bubbles.
 

Tom Barr

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gsjmia;107202 said:
Tom, I don't have any scientific knowledge or back round to add or comment on what you said, but I do know that beverage carbonation takes place in the carbonator tank under about 45 lb's of pressure generated by the cabonator pump.

It seems me that water can only absorb so much Co2 at ground level atmospheric pressure and in order to absorb more it must be done under increased pressure. The inverse is true when you pop a soda can and get carbonated bubbles.

Yes, same thing with Beer etc.
Beer folks are picky about bubbles and color, clarity etc.

I should be easily about to measure the O2 and the CO2(via pH) the next time I do a large water change(on my own tanks as well as client's).
I can estimate the volume of gas per min being added easily using the inverted flask method and then the build up volume also over time inside the chmabers, since I can measure them and obtain the volume vs time for a rate of filling.
 

Matt F.

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This is an overly simplistic question: does water get "stale." Do you think plants just get tired of the same water recirculating over and over again? Any way to measure this? Maybe water change water give the plants the equivalent of a "breath of fresh air?" I'm pretty sure ventilation helps grow mary jane plants (maybe prevents mold and fungus growth, too...

IDK prob unrelated, but questions none the less.
 

Tom Barr

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So the rates of change in the reactor were measured.

The CO2 went up in the sump once the water stopped flowing in, but got NOWHERE near the CO2 saturation most have claimed.
Since the sump recirculates the CO2 reactor water, it's typically about 6.3 pH when the filter is running water through it, and about 6.5 in the tank.
when the filter was shut off, the level was 2" inches down, about 1 hour later, cramming a lot of gas in there(500mls per 2 minutes)?
10 inches

That's a lot of gas and cannot be due to impurities in the CO2 supplies.

The pH dropped to about 5.6-5.7 after 30 minutes and it tooks another 30 minutes to drop to 5.5.

Why?
I thought CO2 dissolves in a few seconds like 5 seconds according to many people?

Why?

Apples and Oranges.

They are comparing a bubble as it SLOWLY floats up at low CO2 concentrations.
This system is blasting the CO2 and the CO2 concentration is high.

Gas or any chemical flux follows Fick's 1st law of Diffusion:
J = -DA (Delta)c/(Delta)x
Where
J=Net rate of diffusion (gms or mols/unit time)
D = diffision coefficient for the diffusing solute
A = area of the membrane
(Delta) c = concentration difference across the membrane
(Delta) x = thickness of the membrane

Since the concentration changes and changes a lot inside the reactor, more is not being dissolved to that 2" level and the gas gap inside increases.
This slows the gas's rate of diffusion into the water.

It has to and Fick's law describes that it will.

So what happened when I restarted the filter again?
What do you think?

The gas bubble inside the chamber rapidly(about 4-5 minutes) dissolved into the water the level went from 10" back to a little under 2".
Difference? Concentrational changes alone.

This could not have changed:

1. D = diffision coefficient for the diffusing solute
2. A = area of the membrane/cross sectional area

This did change by a large factor:
3. (Delta) c = concentration difference across the membrane


This did not change:
(Delta) x = thickness of the membrane

So there's another issue going on, according to some aquarist, they claim that the saturation point for CO2 in water is 1500ppm or thereabouts.
This is true, but they forgot a very important factor in this statement: the rates of degassing.
If I have a nice wet/dry filter with air vents, I can dissolve a lot of gas into water without ever building up much CO2 ppm.
Yes, it dissolves, but never accumulates.

In a tank without a wet/dry filter and/or modified to minimize degassing, this will have a very different result, even though the gas and tank volume are the same, let's assuem the other stuff EXCEPT the degassing part is similar.

What goes in, must come out, if the gas is NOT dissolving.
This is a 2 box model.

So while we can say things about the maximum CO2 ppm water will hold theoretically in a sealed system, reality if quite different.
Our aquariums are degassing CO2 and like Fick's 1st law, the higher the concentration in the water, the greater the flux OUT of the water.
So the CO2 does not reach 1500 ppm easily and likely never even comes close in my own tanks. It's starting to degas MUCH faster as the concentrations rise.
Wet/dry chambers and reactor chambers are similar, the gas in solution will degass more as the ppm's increase.
If you suddenly add fresh "unstale" water as Matt suggest, this gas will quickly dissolve back into solution.

So Fick's 1st law applies in BOTH directions, dissolving and degassing.
Since degassing rates will be different for every tank, this is a tougher issue to pinpoint.
This build up of gas in solution and degassing in also not linear, it's exponential as time increases, it gets harder and harder to hit the 100% saturation level.
Again the Fick's 1st law predicts this.

O2?

It's tough to dissolve into water.
And there's not much of it, and certainly not enough to cause such dramatic changes inside the reactor in the sump test.
You can use cold water and sump and this will add super saturation levels of O2 also to see if the reactor will degas O2.
Then warm it up before turning on the filter pump again.

I do not think there's enough O2 to do what I saw, you might be led to think this over the course of the day as a few hours of higher than 100% are reaches in the water.
Again, a 2 box model, as some goes into solution, O2 is going out. But 1-2 ppm vs say 50 ppm? That's a much larger difference.
And CO2 easily changes that much if you add it only during the day light cycle.
O2 only changes 1-2 ppm. This seems like a more logical approach than claiming the CO2 magically dissolves in a few seconds, observations clearly show something else is going on.
 
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Allelochemicals are secreted from plants as a way to inhibit competition from both conspecific and nonspecific organisms which can include other plants, bacteria, and fungi. (Ceratophyllum demersum [hornwort], for example, is a plant known to secrete such allelochemicals that inhibit the growth of algae and cyanobacteria.) These chemicals inhibit growth by binding to and interfering with physiological mechanisms. When a large water change is performed, the concentration of allelochemicals in the water are reduced. Thus, with a lower concentration gradient in the water, the allelochemicals that have been absorbed by the plant will make it's way out, supposedly through passive diffusion. When these allelochemicals are reduced, it can now re-utilize its physiological functions and the observed growth spurt occurs. This is why water changes increases the rate of plant growth.
 
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Tom Barr

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Solcielo lawrencia;111758 said:
Allelochemicals are secreted from plants as a way to inhibit competition from both conspecific and nonspecific organisms which can include other plants, bacteria, and fungi. (Ceratophyllum demersum [hornwort], for example, is a plant known to secrete such allelochemicals that inhibit the growth of algae and cyanobacteria.) These chemicals inhibit growth by binding to and interfering with physiological mechanisms. When a large water change is performed, the concentration of allelochemicals in the water are reduced. Thus, with a lower concentration gradient in the water, the allelochemicals that have been absorbed by the plant will make it's way out, supposedly through passive diffusion. When these allelochemicals are reduced, it can now re-utilize its physiological functions and the observed growth spurt occurs. This is why water changes increases the rate of plant growth.

This is not true in planted aquariums and has never once been demonstrated in any natural lake or pond or river/stream etc.
They ground up various plants, and added those or the purified chemicals into test wells.

See both Ole's comments as well as my own on the subject:
http://www.barrreport.com/showthrea...-any-significant-effect-on-algae-in-aquariums

A simple control is to add activated carbon to the aquarium, see the same/similar effects?
No, no one has ever reported such a response.
In fact, many have used activated carbon for many years in planted tanks and not noted any impact on plant growth.

I am one of those people, but there are many many others.

Without specific concentrations of the chemicals, as well as a dose response curve, this offers little information. Additionally, what a plant gives off in nature and in the aquarium will vary greatly tank to tank, the water change effect does not. Also, what are the odds that all 400 plant species we commonly keep all have the same chemicals and that the chemicals all illicit the same response at the same concentrations?

A few trillion to one.

The observations are as such: in most all cases, large water changes(frequency can be daily or weeks in between) helps plants grow much better, every one from ADA to the newbie has seen this.

For such wide observation facts, whatever hypothesis needs to be able to address that prior, to any test. You can add a wide range mix of activated carbon that will remove all sizes of organic allelopathic chemicals. This is a standard method for controls in allelopathic plant research FYI. How do I know? I've done it and other students I know did it.
 
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What about this hypothesis: the lowering and increasing of pressure from the water during the water changes is what causes plants to grow faster. If this is true, then simply raising a patch of plants near the water surface for a few minutes and then dropping it back down would increase growth. I'd like to reject this hypothesis but don't have potted plants that I can experiment with right now. One control pot and one experiment pot would suffice.

I'm still loving the nanobubble hypothesis, btw. There isn't enough information about it that would explain why they persist for months without ever dissolving or why they can do some incredibly amazing stuff.
 
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