KCl use in Aquaponics

[Eric Warwick]

This is a thread jack from the comment section of http://community.theaquaponicsource.com/group/artificiallighting . Here's the transcript from the sicko's Jon and Vlad, along with TCLynx and myself. (Read from the bottom.)

Vlad: TC, just out of curiosity...why do you say "in a pinch"? Don't folks salt their systems with NaCl for the chloride ions (tonic for the fish, mitigating nitrite poisoning blabla...)? Potassium chloride seems like a grand way to add K for the plants and provide some chloride ions for the fish at the same time...Is there any reason you know of that this would not be so?

(Jon, cue the music and put your ski mask on ...

TCLynx: Potassium Chloride can work to provide potassium in  a pinch but for me if the pH is fine, I'll usually use some seaweed extract to also get trace elements along with the potassium.As to the tomatoes and flowering.  Toms where I live are a spring and fall crop since summer is too darn hot.  Now we usually don't get the super extreme heat but since I'm in a humid climate it doesn't usually cool off enough at night for good flower/fruit set during the extreme heat of summer.  If you can keep the plant alive and well through the extreme heat, then once the temps come down a bit and you can get the right differential between night and day you should hopefully start seeing some tomato production.

Me: Jon, yes you could, but it's not as efficient as a K buffer. Ultimately, if your pH is good, then your nutrients are going to be absorbed better, which equals less deficiencies. I think, ultimately, if you're making your own nutrient solutions (hydroponic) then KCl would work. I guess it's cheaper to use Calcium Bicarbonate to buffer as well. Anyways, whatever works. 

            Comment by Jon Parr yesterday

Excellent. On the potassium issue, could one use potassium chloride? It certainly is cheap, just paid $12 for 50 lbs, and it's 51% K. Borderline threadjacking, here

Vlad: TC, just out of curiosity...why do you say "in a pinch"? Don't folks salt their systems with NaCl for the chloride ions (tonic for the fish, mitigating nitrite poisoning blabla...)? Potassium chloride seems like a grand way to add K for the plants and provide some chloride ions for the fish at the same time...Is there any reason you know of that this would not be so?

(Jon, cue the music and put your ski mask on ...

TCLynx: Potassium Chloride can work to provide potassium in  a pinch but for me if the pH is fine, I'll usually use some seaweed extract to also get trace elements along with the potassium.As to the tomatoes and flowering.  Toms where I live are a spring and fall crop since summer is too darn hot.  Now we usually don't get the super extreme heat but since I'm in a humid climate it doesn't usually cool off enough at night for good flower/fruit set during the extreme heat of summer.  If you can keep the plant alive and well through the extreme heat, then once the temps come down a bit and you can get the right differential between night and day you should hopefully start seeing some tomato production.

Me: Jon, yes you could, but it's not as efficient as a K buffer. Ultimately, if your pH is good, then your nutrients are going to be absorbed better, which equals less deficiencies. I think, ultimately, if you're making your own nutrient solutions (hydroponic) then KCl would work. I guess it's cheaper to use Calcium Bicarbonate to buffer as well. Anyways, whatever works. 

[Jon Parr]

Excellent. On the potassium issue, could one use potassium chloride? It certainly is cheap, just paid $12 for 50 lbs, and it's 51% K. Borderline threadjacking, here

[Jon Parr]

Thankyou Eric, and I was just getting started over there

[TCLynx]

LOL.

I once asked the question about using potassium chloride instead of salt but I never really got an answer back from the people who know more about fish than I do.

It seems to make sense to me that the potassium chloride would work to provide the chloride mitigating nitrite poisoning when dealing with such cycling up issues, but as I am definitely not a chemist, please do more research and don't take my word for it.  However, I don't know that one would want to constantly be adding the chloride if using potassium chloride for the potassium supplementation.

Now there are those out there who try to tell people NOT to supplement potassium but I'm guessing their experience will have a different effect since the source water on a pacific Island and using coral sand as a buffer might actually supply enough potassium that they need not supplement with it.  I've personally definitely found I need to supplement potassium and other trace elements regularly in my systems.  Before I found a local source of seaweed extract, I did use potassium Chloride a few times in my old system.  Now it is possible that good quality sea salt might provide enough potassium and trace elements that other supplements might not be needed but I haven't tried it.

[Eric Warwick]

I would think that KCl would be more expensive than NaCl, so the use of KCl to mitigate Nitrite poisoning would be unjustifiable. When trying to supplement with KCl it might make sense. However, it is probably cheaper to use seaweed extract. So, I would think that having KCl would not make economic sense. Besides, plants need Na, too. 

[Vlad Jovanovic]

Eric, I think a lot of 'what makes economic sense' depends on where one lives. But, I agree that it might be better to use the KCl in a K supplementing role rather than a nitrite mitigating one. If for no other reason than just to be on the 'safe' side (since the amounts used will be much smaller... ppm's rather than ppt's).

But, it would seem that any long term 'risks' you run as far as salinity or chloride issues when mitigating brown blood disease with KCl, you run the same risks anyways with NaCl.?

Now, one could argue the 'too much potassium' line of thought, but then... don't we calm peoples trepidations about using NaCl by citing studies that show that Na and K are largely interchangeable in plant (and human) biology? 

IDK guys, unless K is lethal to fish at those concentrations 1-2ppt KCl salt (divided by roughly half for the K), I'm not really seeing a drawback? That's not to say that there might not be one...

Other than a theoretical cation imbalance plant-wise, which again seems unlikely especially with my water, (Na is an alkaloid metal cation similar to K) I'm just not seeing any drawbacks. Maybe someone else can?

[Jon Parr]

Well, by way of experiment, I'm going to start (actually already have for the last two weeks) dosing my tanks at 1/2 ppt NaCl ($5/50 lb), plus 1/2 ppt KCl ($15/50 lb), just for fun. Both are very cheap, and I suppose I need to invest in salinity meter of some sort. Btw, plants loved the KCl, unless that was my imagination, and I can't say the same for NaCl treatments in the past.

[Vlad Jovanovic]

Very, very cool. If i had to bet, (and I'm not much of a gambling man) I'd say this ones a zinger...

Jon Parr said:

Well, by way of experiment, I'm going to start (actually already have for the last two weeks) dosing my tanks at 1/2 ppt NaCl ($5/50 lb), plus 1/2 ppt KCl ($15/50 lb), just for fun. Both are very cheap, and I suppose I need to invest in salinity meter of some sort. Btw, plants loved the KCl, unless that was my imagination, and I can't say the same for NaCl treatments in the past.

[Vlad Jovanovic]

Remember that on a per weight basis NaCl is 60.66% Cl

Calculate the molecular mass (MM): 
MM = 22.99 + 35.45 = 58.44

Calculate the total mass of Na present: 
1 Na is present in the formula, mass = 22.99

Calculate the percent by weight of Na in NaCl: 
%Na = (mass Na ÷ MM) x 100 = (22.99 ÷ 58.44) x 100 = 39.34%

Calculate the total mass of Cl present: 
1 Cl is present in the formula, mass = 35.45

Calculate the percent by weight of Cl in NaCl: 
%Cl = (mass Cl ÷ MM) x 100 = (35.45 ÷ 58.44) x 100 = 60.66%

 

KCl works out to about 47.5% Cl by weight, so depending on how your going about the additions, you may be adding less salinity than with your NaCl (since Cl is the determinant of salinity and there is less Cl by weight in the KCl). I'm sure you've already taken this crap into account since you were active in the thread where it was gone over in, but figured I'd put it out there again anyways.

I may, or may not go fishless all winter and am also thinking about adding KNO3 to the mix (home made of course from urine, straw and wood ash, refined and "measurable"). I figure I've got the phosphate recovery down pat with the Struvite reactor, it's working great and I've about learned about all I can/need....So, I think it's time to move on so to speak...So KNO3 seems like the next logical arena in the 'pee-ponic philosophy'. Just like the phosphates from struvite, it would be immediately bio-available to the plants, so the bacteria can slumber/hibernate all they want...Nitrates and potassium a winning winter combination...no salts build up, no bacteria action 'required', no hydro stores, no ammonia burn and no goddamn fish to mess with (though KNO3 should be fish safe), no fancy equipment and totally sustainable (as long as I'm alive, drinking and pissing)...that's the idea anyways...

At any rate... you'll be adding more salinity with 1ppt of NaCl than you would be with 1ppt of KCl...

[Vlad Jovanovic]

Vlad Jovanovic said:

Remember that on a per weight basis NaCl is 60.66% Cl

Calculate the molecular mass (MM): 
MM = 22.99 + 35.45 = 58.44

Calculate the total mass of Na present: 
1 Na is present in the formula, mass = 22.99

Calculate the percent by weight of Na in NaCl: 
%Na = (mass Na ÷ MM) x 100 = (22.99 ÷ 58.44) x 100 = 39.34%

Calculate the total mass of Cl present: 
1 Cl is present in the formula, mass = 35.45

Calculate the percent by weight of Cl in NaCl: 
%Cl = (mass Cl ÷ MM) x 100 = (35.45 ÷ 58.44) x 100 = 60.66%

 

KCl works out to about 47.5% Cl by weight, so depending on how your going about the additions, you may be adding less salinity than with your NaCl (since Cl is the determinant of salinity and there is less Cl by weight in the KCl). I'm sure you've already taken this crap into account since you were active in the thread where it was gone over in, but figured I'd put it out there again anyways.

I may, or may not go fishless all winter and am also thinking about adding KNO3 to the mix (home made of course from urine, straw and wood ash, refined and "measurable"). I figure I've got the phosphate recovery down pat with the Struvite reactor, it's working great and I've about learned about all I can/need....So, I think it's time to move on so to speak...So KNO3 seems like the next logical arena in the 'pee-ponic philosophy'. Just like the phosphates from struvite, it would be immediately bio-available to the plants, so the bacteria can slumber/hibernate all they want...Nitrates and potassium a winning winter combination...no salts build up, no bacteria action 'required', no hydro stores, no ammonia burn and no goddamn fish to mess with (though KNO3 should be fish safe), no fancy equipment and totally sustainable (as long as I'm alive, drinking and pissing)...that's the idea anyways...

At any rate...to not jack a jacked thread....... you'll be adding more salinity with 1ppt of NaCl than you would be with 1ppt of KCl...

[Eric Warwick]

You said it, Vlad, that's kind of (emphasis on kind of) what I was hinting at. That KNO3 idea is good, I think Hydroponic Food Production, by Howard M. Resh, suggested it as a good K supplement and a good source of Nitrate Nitrogen. Anyways, I hope it works well.

[Eric Warwick]

Vlad:

"At any rate...to not jack a jacked thread....... you'll be adding more salinity with 1ppt of NaCl than you would be with 1ppt of KCl..."

To catch a thread-jacker. 

[Jon Parr]

Thanks Vlad. I knew there would be a weight difference between the two, but hadn't penciled it out yet. The bigger question I have, is the ratio between Na and K demand in the plant, which of course is different for different plants and phase of growth. But on the average, I'm guessing much more K is drawn up than Na, especially if both are available.

I think your struvite reactor is brilliant, and I've got some piss aging as we speak (such a pleasant thought...), and I'm very interested how the straw and ash relate. I'm assuming the humonia/ash is quite base. Do you simply add HCL acid to bring pH into range? And does HCl also raise the chloride count of the water, measurable with a salinity meter? I used to measure salt content of a marine aquarium with a specific gravity measure, just a graduated plastic dial that floats in a plastic box. Any idea if that would work to measure 1 ppt salt? Probably not, since it's designed for seawater. I'll have to dig it out and look at it.

I've been discussing your struvite reactor with a fellow AP guy here in town, who is working on growing algae with piss for space missions (he works for NASA). They are also working with a photovoltaic clear (actually pink/orange) membrane that harvests infrared and green light for electricity, but allows photosynthesis light to pass through. How cool is that?!

[Eric Warwick]

And this is why I want to work for NASA eventually.
Jon Parr

I've been discussing your struvite reactor with a fellow AP guy here in town, who is working on growing algae with piss for space missions (he works for NASA). They are also working with a photovoltaic clear (actually pink/orange) membrane that harvests infrared and green light for electricity, but allows photosynthesis light to pass through. How cool is that?!