glutaraldehyde

[Sheraaz Essak]

Has anyone got any feedback on this product from "Aqua design" I usually look at the % of glutaraldehyde in a product I'm buying, as nothing was stated on the label or website, I emailed the company asking for some basic information, I.e the glutaraldehyde percentage used in their product. Unfortunately they weren't willing to disclose the % claiming their formula is a secret which has raised doubts on the effectiveness of their product.

Anyone that's actually used this and has some feedback, I'd really appreciate it, thank you in advance.

 

[MichaelJ]

While there might be a minuscule boost to CO2 availability - say the oft quoted 2 ppm in total over the course of like 8 hours after the recommended dosing of say Excel - but no one seems to know what the availability curve is... Is it blown off in 2 hours or 6 hours ... in which case it will amount to an average increase of 0.3 ppm/hour if it would be a linear dissipation curve (which it definitely isn't) ... I have a hard time to see how that amount could have any significant benefits for the plants.

That's correct, the ppm unit is misleading.

It’s not misleading if we know what we are talking about - ppm is a perfectly meaningful way to describe the situation as long as we are careful about not making the erroneous comparisons.

In air, it is parts (CO2 molecules) per million (million air molecules).

100% correct. This ppm (426) number tells us how many parts of carbon dioxide there are in one million parts of air regardless of volume - be it under 100 atm of pressure or at 1 atm.

And this relates to glutaraldehyde because...?

John, there is no relation at all, but we are having fun aren’t we?

Cheers,
Michael

 

[simon_the_plant_nerd]

I suppose some confusion comes from the fact that PPM is just “in 1,000,000 x, how many are y?”

In one million marbles, how many are red marbles? Ten red marbles would be 10ppm.

This has nothing of course to do with mg/litre. The weight of the marbles or the capacity are not relevant to what we are expressing here.

In the specific use case of molecules of a substance in water, then mg/l could become equivalent to ppm as 1litre of water weighs 1kg (or 1 million milligrams). But if it’s not water we are considering, then it no longer makes sense.

What has this got to do with gluteraldehyde? Don’t know really but I’m definitely having fun. I think.

EDIT: PPM is a dimensionless unit. Give me my A!

 

[Andy Pierce]

426 ppm CO2 in air is expressed by volume. 1 to 30 ppm CO2 in water is expressed by weigh
Unit conversion from by volume to by weight is not simple. Parts Per Million (ppm) Converter
My calculation shows that 426 ppm CO2 by volume is equivalent to 826 mg /m3 or 0.826 mg/l by weight in air. So CO2 concentration in water is often higher than in air, but the diffusion rate to plant in water is much slower.

Um... well that sends the conversation sideways.
Although the result of the calculation is on the face of it unexpected, upon reflection it is not too surprising that the density of gasses is going to be lower (generally) than the density of liquids. True fact that diffusion in gasses is faster than diffusion in liquids, but CO2 distribution in an aquarium is driven by water circulation, i.e. CO2 is distributed primarily mechanically rather than by diffusion. That's also why flow is important in an aquarium - mostly for distribution of oxygen for livestock, but also CO2 for plants.

To the density piece... (and just having funzies here) in a gas, the volume is related to the number of molecules so in air 426 ppm CO2 (by volume) means that for every million molecules of gas in air 426 will be CO2. In the water phase of an aquarium, 30 ppm CO2 (30 mg/L) is 0.000681 M, but the concentration of water is 55.5 M, so for every million molecules in the liquid, only 12 will be CO2.

 

[MichaelJ]

I suppose some confusion comes from the fact that PPM is just “in 1,000,000 x, how many are y?”

In one million marbles, how many are red marbles? Ten red marbles would be 10ppm.

This has nothing of course to do with mg/litre. The weight of the marbles or the capacity are not relevant to what we are expressing here.

In the specific use case of molecules of a substance in water, then mg/l could become equivalent to ppm as 1litre of water weighs 1kg (or 1 million milligrams). But if it’s not water we are considering, then it no longer makes sense.

Good explanation and analogy.! You would have passed an exam paper I once had to write up for first year students on a very similar topic …. If you would have said that ppm is a dimensionless unit you would have gotten an A from me …

Cheers,
Michael

 

[simon_the_plant_nerd]

Good explanation and analogy.! You would have passed an exam paper I once had to write up for first year students on a very similar topic …. If you would have said that ppm is a dimensionless unit you would have gotten an A from me …

Cheers,
Michael

Decent. I hope my analogy helped some of the other simple brains like myself.

 

[tiger15]

That's correct, the ppm unit is misleading. In air, it is parts (CO2 molecules) per million (million air molecules). In water, ppm means mg /l. So we can not compare directly the two ppms. The calculation seems to be right, I also get 0.83 mg/l for CO2 in atmospheric air. The diffusion rate is 10,000 higher in air.

ppm by volume or by number of molecules in gases is equivalent due to Avogadro's law that states that "equal volumes of all gases, at the same temperature and pressure, have the same number of molecules."

Avogadro's law - Wikipedia

en.wikipedia.org

And this relates to glutaraldehyde because...?

The discussion is relevant in that there is a debate on how much CO2 boosting is achieved by glut dosing. IMO none as I haven’t seen any evidence to less than minuscule 2 ppm at the recommended Glut dosing rate if it can be proven one day . One poster mentioned that there was C13 tracing of glut into photosynthesis by mass spectrometry. I haven’t seen the research paper and doubt that MS can quantify isotopes.

 

[tiger15]

True fact that diffusion in gasses is faster than diffusion in liquids, but CO2 distribution in an aquarium is driven by water circulation, i.e. CO2 is distributed primarily mechanically rather than by diffusion. That's also why flow is important in an aquarium - mostly for distribution of oxygen for livestock, but also CO2 for plants.

Both circulation (convection) and diffusion distribute gases in air and water, but convection plays a much bigger role. But what we are comparing is how slow plants uptake CO2 in water than in air due to enormous difference in diffusion rate. If plants had gills like fish that can mechanically draw gases by convection, the uptake of CO2 would be a lot more efficient. The atmosphere has 210000 ppm (296 mg/l by weight) O2 versus only 8 mg/l in water, yet fish has no difficulty getting enough O2 than terrestrial vertebrates.

 

[John q]

One poster mentioned that there was C13 tracing of glut into photosynthesis by mass spectrometry

I think Tom Barr and Greg Morin had some discussions about isotopic labeling of Glut but don't think Seachem were prepared to shell out thousands of dollars to fund such research, or if they did then we would have to ask why the results of said research aren't in the public domain.

 

[tiger15]

I think Tom Barr and Greg Morin had some discussions about isotopic labeling of Glut but don't think Seachem were prepared to shell out thousands of dollars to fund such research, or if they did then we would have to ask why the results of said research aren't in the public domain.

The tracing of atom pathways in biochemistry is very complicated and could cost a lot more than $thousands. The scientist who took lifetime to identify the pathways of Calvin cycle earned a Nobel price. There is no financial justification for Seachem to take up the task, besides, the conclusion may turn out to be contradictory to their claim.

 

[John q]

There is no financial justification for Seachem to take up the task,

Yeah agreed, so no point looking for..

C13 tracing of glut into photosynthesis

By the way Greg suggested C14 isotope tracing. $$$$ 😆

 

[tiger15]

Yeah agreed, so no point looking for..

By the way Greg suggested C14 isotope tracing. $$$$ 😆

In Post #7 Ian claimed that someone has done a C13 tracing. Whether it is C13 or 14 tracing is no simple task. Glut can take a pathway of naturally degraded into CO2, uptake and thereby incorporate C13 or 14 into plant tissue.

 

[LMuhlen]

That's correct, the ppm unit is misleading. In air, it is parts (CO2 molecules) per million (million air molecules). In water, ppm means mg /l. So we can not compare directly the two ppms. The calculation seems to be right, I also get 0.83 mg/l for CO2 in atmospheric air. The diffusion rate is 10,000 higher in air.

Pointless as it may be, I think it is a good to add a remark, considering that this topic was brought up. The PPM we use for ferts is not mg/l, as PPM is dimensionless. PPM is mg/kg, and we only adapt it to our hobby as mg/l because the density of water is very close to 1kg/l, so it is numerically the same, and it is easier to visualize for our fertilizing interests.

But with that in mind, there is no justification to compare to mg/l of air, as it has nothing to do with PPM.

If the ~400 PPM in air for CO2 is indeed in molar base, as it probably is since you are saying it is, this number should be even higher in mass base, since the molar weight of CO2 is higher than of O2 and N2, both of which respond for ~99% of the molecules in air. If memory from ages ago serve me right, 1m³ of air is roughly 1kg, so based on your number for concentration in mg/l, the mass weight concentration is ~800 ppm, higher than in water.

 

[tiger15]

Pointless as it may be, I think it is a good to add a remark, considering that this topic was brought up. The PPM we use for ferts is not mg/l, as PPM is dimensionless. PPM is mg/kg, and we only adapt it to our hobby as mg/l because the density of water is very close to 1kg/l, so it is numerically the same, and it is easier to visualize for our fertilizing interests.

But with that in mind, there is no justification to compare to mg/l of air, as it has nothing to do with PPM.

If the ~400 PPM in air for CO2 is indeed in molar base, as it probably is since you are saying it is, this number should be even higher in mass base, since the molar weight of CO2 is higher than of O2 and N2, both of which respond for ~99% of the molecules in air. If memory from ages ago serve me right, 1m³ of air is roughly 1kg, so based on your number for concentration in mg/l, the mass weight concentration is ~800 ppm, higher than in water.

Your math is wrong. The math is complex, so don’t do the math yourself but use the conversion calculator in this link.

Parts Per Million (ppm) Converter

Conversion of units in Parts Per Million (ppm) to miligram per cubic meters and visa versa.

www.lenntech.com

If you pug in 426 ppm for CO2, the calculator will spit out 826 mg/m3. Since 1 m3=1000L, the correct concentration is 0.826 mg/L, which is lower than 1 to 3 mg/L typically found in tank water.

Read the article in the above link from top to bottom. It clarifies the difference between ppm by volume versus ppm by weight, why ppm by weight in water is equivalent to mg/L, why ppm by volume in air is equivalent to ppm by mole, why concentration in air is not expressed in ppm by weight but rather ppm by volume (aka ppmv) and occasionally ug/m3, and so on.

 

[dw1305]

Hi all,

If you pug in 426 ppm for CO2, the calculator will spit out 826 mg/m3. Since 1 m3=1000L, the correct concentration is 0.826 mg/L, which is lower than 1 to 3 mg/L typically found in tank water.

I still think we are in <"Apples and Oranges">* territory, because we are comparing a dense medium (water density ~ 1000 kg/m³) with a much less dense medium (Dry air at 20°C and standard atmospheric pressure (1.013 bar) has a density of 1.204 kg/m³.) <"Air Density">.

*edit what @LMuhlen says.

To the density piece... (and just having funzies here) in a gas, the volume is related to the number of molecules so in air 426 ppm CO2 (by volume) means that for every million molecules of gas in air 426 will be CO2. In the water phase of an aquarium, 30 ppm CO2 (30 mg/L) is 0.000681 M, but the concentration of water is 55.5 M, so for every million molecules in the liquid, only 12 will be CO2.

So that one is the maths that count?

The point I’m driving at is that plants can absorb CO2 more efficiently in the atmosphere than under water not because of higher concentration, but higher diffusion rate in the atmosphere. Due to difference in diffusion rate, CO2 in air, unlike in water, can never be depleted by photosynthesis.

but the diffusion rate to plant in water is much slower.

and that is the other important bit? I know that plants can definitely grow more quickly with access to atmospheric CO2, and plant growth is a direct measure of CO2 incorporation during photosynthesis.

cheers Darrel

 

[LMuhlen]

If you pug in 426 ppm for CO2, the calculator will spit out 826 mg/m3. Since 1 m3=1000L, the correct concentration is 0.826 mg/L, which is lower than 1 to 3 mg/L typically found in tank water.

My point is that mg/L is not the same as PPM_mass (which is mg/kg). In water, since the density is very close to 1kg/L, both values (PPM and mg/L) are numerically equal, but they are still different in meaning. One is mass/mass, the other is mass/volume. The concentration of CO2 in PPM_mass for air is much higher than the concentration in PPM_mass in water.

Concentration should preferably be used in molar base or mass base. Concentration by volume is affected by things that change the volume, such as temperature and pressure, so it is "inferior". We use it for our daily routine because it is easy, but it is less precise. We actually have issues with this when we add salts to water and don't know the final volume of the solution, then we need to "top with water until a known volume". If we used a mass based concentration, we would just do the math.

Starting from your found value of 826 mg/m³ of air, using the value of 1,29 kg/m³ as air density, the concentration of CO2 in air is 640 PPM_mass, much higher than the before mentioned 3 PPM_mass in water.

I could be way off here, but my guess is that, for the plants, what matters is the partial pressure, so that would make the PPM_molar unit the important one.

 

[tiger15]

My point is that mg/L is not the same as PPM_mass (which is mg/kg). In water, since the density is very close to 1kg/L, both values (PPM and mg/L) are numerically equal, but they are still different in meaning. One is mass/mass, the other is mass/volume. The concentration of CO2 in PPM_mass for air is much higher than the concentration in PPM_mass in water.

Concentration should preferably be used in molar base or mass base. Concentration by volume is affected by things that change the volume, such as temperature and pressure, so it is "inferior". We use it for our daily routine because it is easy, but it is less precise. We actually have issues with this when we add salts to water and don't know the final volume of the solution, then we need to "top with water until a known volume". If we used a mass based concentration, we would just do the math.

Starting from your found value of 826 mg/m³ of air, using the value of 1,29 kg/m³ as air density, the concentration of CO2 in air is 640 PPM_mass, much higher than the before mentioned 3 PPM_mass in water.

Your math is correct, but the concept is not. When comparing plant exposure to CO2 availability (concentration) in different media, it should be based on the same volume of exposure, not mass.

It is unfair to compare one unit mass of air that occupies 1000 times more volume than that of water (1 kg/1000L versus 1 kg/L), meaning there is 1000 times more plant tissue exposure to CO2 in one unit mass of air than water.

I still don't fully understand why plants can extract CO2 in air more efficiently than in water despite comparable CO2 concentrations. Only a fraction of terrestrial leaves, the stomata, can exchange gases whereas all plant tissues under water can exchange gases. So this balance off higher gas diffusion rate in air than in water. In green house operations, plant growth can be stunt if supplemental CO2 is not provided, so it is not unlike planted tank operation. Go figure.

 

[LMuhlen]

I edited my post, but maybe too late. I think that plants care about partial pressure, so the best unit would be PPM_molar, which is the 400something ppm we always used.

 

[dw1305]

Hi all,

In green house operations, plant growth can be stunt if supplemental CO2 is not provided,

They don't exactly stunt, it is just that the growth of Tomatoes etc. is sub-optimal at ambient CO2 levels. You can definitely get local depletion of CO2 in glasshouses, this is because they are (to some extent) sealed structures.

If you make sure that PAR, water and nutrients are non- limiting Tomatoes can make use of at least <"1200 ppm CO2">. <"https://www.vegetables.bayer.com/au...nd-co2-for-tomatoes-in-protected-culture.html">

When comparing plant exposure to CO2 availability (concentration) in different media, it should be based on the same volume of exposure, not mass.

It is unfair to compare one unit mass of air that occupies 1000 times more volume than that of water (1 kg/1000L versus 1 kg/L), meaning there is 1000 times more plant tissue exposure to CO2 in one unit mass of air than water

But surely there is? Because the air is a much less dense medium, meaning that large volumes of CO2 rich air are available to the plant.

Isn't it the same argument as distributing added CO2 via flow in the aquarium, except in this case we have atmospheric gases and they are continually in motion and inexhaustible?

You can easily <"deplete the CO2"> in a water body (even outside), via photosynthesis.

cheers Darrel

 

[tiger15]

I edited my post, but maybe too late. I think that plants care about partial pressure, so the best unit would be PPM_molar, which is the 400something ppm we always used.

In air, ppm by volume and by molar is the same due to Avogadro law.

Hi all,

They don't exactly stunt, it is just that the growth of Tomatoes etc. is sub-optimal at ambient CO2 levels. You can definitely get local depletion of CO2 in glasshouses, this is because they are (to some extent) sealed structures.

If you make sure that PAR, water and nutrients are non- limiting Tomatoes can make use of at least <"1200 ppm CO2">. <"https://www.vegetables.bayer.com/au...nd-co2-for-tomatoes-in-protected-culture.html">

But surely there is? Because the air is a much less dense medium, meaning that large volumes of CO2 rich air are available to the plant.

Isn't it the same argument as distributing added CO2 via flow in the aquarium, except in this case we have atmospheric gases and they are continually in motion and inexhaustible?

You can easily <"deplete the CO2"> in a water body (even outside), via photosynthesis.

cheers Darrel

Atmospheric CO2 is not exhaustible in open environment but can happen in green house containment. On the other end, indoor CO2 can build up quickly to 1000-2000 ppmv in a crowded room, and in the confine of a car if outside circulation is off.

CO2 is exhaustible in both open water and fish tanks, so the contrast has something to do with slow gas exchange rate in the water air interface. In other words, Henry law equilibrium is not achieved rapidly, but slowly.

 

[LMuhlen]

In air, ppm by volume and by molar is the same due to Avogadro law.

What you are using, mg/L, is not PPM by volume. PPM by volume would be something like cm³/m³ or mm³/L. The molar concentration of CO2 in air is the value close to 400 PPM. That would be the number to use, if partial pressure was indeed the most important factor.

Converting from mg/L to PPM_molar involves the molecular weight. Since CO2 is the heaviest molecule involved, its fraction is reduced when converting from mass to moles. If my algebra is correct, 3 PPM_mass of CO2 in liquid water converts to something like 1,22 PPM_molar, making the difference between CO2 in water and CO2 in air even larger. Pressure under half a meter of water would maybe increase partial pressure and help the CO2? Even then, that is only 0,05 atm.