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

[Vlad Jovanovic]

Jon, I wasn't so much meaning the weight difference between a given volume of the two, but rather...in say one gram of NaCl there is more salinity (Cl) than in the same one gram of KCl...

Wow, those PV cells sound ridiculously cool. That's a really neat idea.

Yeah, that whole Na/K uptake deal is pretty...well...you'd be hard pressed to find any meaningful across the board 'averages'. Many of those studies seem to deal with really quite narrow/specific circumstances. Like K starving the plants to induce Na uptake. Add to that the fact that some cultivars are natrophiles, while others natrophobic along with a host of other 'special circumstances' and all of a sudden Na is not looking so hot or even interchangeable 'generally' across the board anymore...I think you are absolutely right in your thinking that "much more K is drawn up than Na, especially if both are available"...

Yep, both humonia and ash (or rain/distilled water filtered through ash) are very high pH...and might require an adjustment (yes, I like to use HCL for this too)...or might not if your adding them to a system that needs buffering up. I've filtered water through a barrel full of straw and rocks (they only serve as a mechanical filter and do nothing chemically for the process) and hardwood ashes and gotten KOH. This is pretty straight forward and very easy to do. Skill level one.

http://community.theaquaponicsource.com/profiles/blogs/determining-...

But, the KNO3 seems much more involved and time consuming, but the reward is a product that is 'superior' in many applications. Basically you use the straw as a medium to soak with humonia. "Ferment" it using the very same nitrifying bacteria that we have in our AP systems (this takes lots of time unfortunately, but I'm trying to work a way around that). Then you rinse (leach) the the nitrate laden fermented straw/humonia mix (it's mostly calcium nitrate at this point) then run that liquid through wood ash to convert it to potassium nitrate...then dry (evaporate the water and harvest the crystallized KNO3 that's left)...That's pretty much it in 100 words or less...

I have no idea, but they probably sell hydrometers, or those newfandangled refractometers of various sensitivities..? 

Thanks for the reactor comment...I'm pretty happy with the thing. works well for processing "large-ish" batches (all things being relative of course) quickly, and building the thing out of stuff I had lying around was pretty fun... the test runs though, were done in a plastic measuring cup (1 litre) and mixed with a stick. Worked just fine for very small runs. 

Sorry if I skipped anything, it's been a super long farming day...

@Eric, thanks for the well wishes...and I hope you get to work for NASA some day :)

Jon Parr said:

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?!

[Chris Carr]

I didn't want to jack the thread but since you mentioned the homebrewed KNO3 again... I will. Maybe a thread makes more sense.

I found a wikipedia reference to be interesting enough which discussed a few known old school techniques used for this. http://docsouth.unc.edu/imls/lecontesalt/leconte.html

One interesting advantage to the process is that I don't see why you couldn't use the effluent from the struvite reactions as well. It also got me thinking if the nitrifying bacteria can survive the much harsher, concentrated conditions in the straw, why could you not setup a sump and constant flowthru bio filter (lets say from 2x5gallon buckets to test) filled with straw or some other medium (maybe even something inorganic?) and just keep topping it up with humonia. If the goal is just to convert to nitrate and concentrate the solution maybe it wont take that long at all. When is best and how to harvest would need a bit of thinking. Also is it possible to integrate the ash into the "reactor" from the start or is it best to be left as part of the harvesting process?

Just some thoughts on the idea anyway. 

[Eric Warwick]

@Chris: good point. At some time or another I was looking into making a "deconstructed" pee-ponics set-up. I think you could use Nitrifying Bacteria to produce NO3 (aq).( aq means dissolved in water by the way.) Then you could conceivably use it for a nutrient solution. Start a thread if you like, maybe in the thread jackers-jackers group .

[Vlad Jovanovic]

Thanks for the link Chris. That's the one I fist came to, and invariably always led back to... LeConte's description of the process in 1862 seems to be the one that is drawn from most often in the English speaking world.

It seems like it should be possible to incorporate ash into the reactor directly, but I'd like to keep those separate operations for now. Apparently, when your pouring the calcium nitrate rich liquid over the ashes, or combining already leached potassium hydroxide into that same liquid a white haze should be seen , and this white precipitate (calcium hydroxide or 'curds' as it was called) would slowly sink to the bottom of the barrel. If the solution contained an excess of calcium nitrate, the product was termed 'in the grease.' An excess of woodashes produced a condition called 'in the lye.' 

The wood ash leachate was poured into the mother liquor until the white curds could no longer be seen precipitating out of solution. The remaining solution thus contained the still soluble potassium nitrate...Since I've never done this before, I like the clearly delineated visible cues as to what's going on, and when you are done 'converting' that the 'extra step' of keeping the ashes separate gives you.

Also, I'm not sure how the pH variable would play out when adding ashes directly to the bacteria's strawbed/media environment? (Slowing things down, perhaps)?

Yes, a separate thread would make sense (albeit, a bit ironic given the name of this group :)

Wow Eric,A threadjacker's-jackers group eh? I'm seeing it as a place where good ideas can be saved from the sprawling mass of half coherent off topic ramblings...being 'jacked' themselves (this time by upright members of the community), organized, reformed, properly tagged and released back into the mainstream forum community...Naw. :)

Chris said:

I didn't want to jack the thread but since you mentioned the homebrewed KNO3 again... I will. Maybe a thread makes more sense.

I found a wikipedia reference to be interesting enough which discussed a few known old school techniques used for this. http://docsouth.unc.edu/imls/lecontesalt/leconte.html

One interesting advantage to the process is that I don't see why you couldn't use the effluent from the struvite reactions as well. It also got me thinking if the nitrifying bacteria can survive the much harsher, concentrated conditions in the straw, why could you not setup a sump and constant flowthru bio filter (lets say from 2x5gallon buckets to test) filled with straw or some other medium (maybe even something inorganic?) and just keep topping it up with humonia. If the goal is just to convert to nitrate and concentrate the solution maybe it wont take that long at all. When is best and how to harvest would need a bit of thinking. Also is it possible to integrate the ash into the "reactor" from the start or is it best to be left as part of the harvesting process?

Just some thoughts on the idea anyway. 

[Jon Parr]

Hehe.

So, in a rash decision to try KCl as a treatment for fish parasites, I just went ahead and added a 3 ppt to a tropical tank containing tilapia, red claws, and pangasius catfish. Why? Well, one of the catfish recently jumped out of the tank and has got cloudy eyes and pale color, I don't know if it's a stress related outbreak, or actual physical damage from flopping on the concrete with those bulging eyes they have. And one of the tilapia is paling, which I have experienced before, always slowly ending in a single weaker and weaker fish that dies, while the remaining tilapia are unaffected. I never treated the previous symptomatic tilapia (lazy, one fish didn't cause a panic), but thought I'd give it a whirl with KCl in lieu of NaCl. Two days, so far so good. There are berried craws, and brooding tilapia, no ill temper among those either. TC never got an answer from her fish experts concerning the substitution of KCl for NaCl, so this experiment should add some data to the puzzle. Cross my fingers.

[TCLynx]

Well I hope to hear some good result Jon. 

Now I have definitely seen drastic results treating tilapia with salt especially when I have a stressed out female that looked like she had fin rot (but it was probably more likely that she was just getting chewed up by the male.)  Anyway, I removed her to a separate tank and salted the system and she recovered quickly.

Now I know that salt helps the fish in a few ways.

A-improving slime coat (not sure which part of the salt takes care of this)

B-being an  electrolyte it helps with the osmotic pressure and allowing the fish to balance themselves better.  This one I figure should be useful by either sodium or potassium chloride.

C-The Chloride ions can bind with the nitrite and help protect the fish from the nitrite and this one I expect can be filled by either.

[Vlad Jovanovic]

TC, in regards to point C ...

I know Sylvia had some gentleman write up a blog or whatever here where that bit about chloride binding to nitrite and all was mentioned...but it appears absolutely untrue. Back when I read that statement, it seemed a little fishy too me (kinda like saying "two negative poles of a magnet will attract one another), so I looked it up and posted/linked the study in the "books, articles and links thread" here it is again (its a very short and easy to understand study)

http://www-heb.pac.dfo-mpo.gc.ca/congress/1994/tomasso.pdf

http://community.theaquaponicsource.com/group/books_documentaries_a...

Chloride mitigates nitrite toxicity by a mechanism called 'competitive inhibition'. There is no "binding" going on between chloride (a negative ion) and nitrite (also a negative ion)...Rather the chloride ions take up space on the fishy's gills where normally the nitrite ions would, effectively blocking the pathway for the nitrite to attach themselves and do their damage.

Same way (competitive inhibition) that say, our 'good' bacteria out compete pythium (or whatever) for space/resources in our AP systems.

Not to be a stickler or a dick, but I see that bit of (mis)info in various places in AP-internet land and well..."we know stuff now"... :)

So the chloride 'blocks' the nitrites from entering/attaching to the fishes system and does not bind the nitrite in any known way.

@Jon...Sweet! Keep us posted (this is exciting in a geek-ish sorta way). 

[Eric Warwick]

Thank you, Vlad, the binding argument never made sense to me. Jon: good luck! I hope to see good results.

[TCLynx]

I expect that bit of mis-information is really mostly due to those of us who don't really understand chemistry that well simply using the wrong terminology when describing that the chloride ions somehow help mitigate nitrite toxicity.  I don't think I ever really fully understood how but only that salting the system to about 1 ppt could help save fish during a nitrite spike.

I'm ok with being corrected by the way, especially when you can explain it better than I.

[Eric Warwick]

Don't worry, I think my chemistry teacher (trained in biology, taught both in the same class.) told me the Chlorine ion bonded to the Nitrite ion. 

TCLynx said:

I expect that bit of mis-information is really mostly due to those of us who don't really understand chemistry that well simply using the wrong terminology when describing that the chloride ions somehow help mitigate nitrite toxicity.  I don't think I ever really fully understood how but only that salting the system to about 1 ppt could help save fish during a nitrite spike.

I'm ok with being corrected by the way, especially when you can explain it better than I.

[Vlad Jovanovic]

@TC Well, it seems that the important thing, really, is that people know that salting the system to about 1 ppt with a chloride salt could help save fish during a nitrite spike.

The next important thing there would then seem to be, that folks know how to go about measuring and weighing how much salt to add to their particular system to get to a given ppt... http://www.aquaponiclynx.com/salt-for-fish-health

Knowing exactly how/why something works is hardly always a necessity...but it sure is nice sometimes :)

 

@Jon, the difference in physical weight you alluded to earlier...Theoretically, a bit more KCl would seem to be called for.... The difference in chloride content, 60.66% for NaCl and 47.5% for KCL would suggest (depending on how you went about dosing and all) that in terms of chloride content relative to NaCl, you might be closer to 2.5ppt.

It may not really matter...that 0.5ppt, but just thought I'd throw it out there, in case it is important to you or your fish.

Hope the Sac tour was fun.

 

 

 

 

[Vlad Jovanovic]

Ok...Jon while your out cavorting around town...I decided to "pencil out" some of the bitch work in the hope that you can then  think about it and choose whether to apply it or not...It is your system after all :)

My hope is to be able to explain this properly (something I'm often not good at)...

So, we've established that when salting for say, nitrite toxicity, it is the chloride ions that we're after.

We've established that the chloride content of NaCl is 60.66% (round 61%)

We've established that the chloride content of KCl is 47.5% (round 48%)

Now... The weight difference between the two...best I can figure...

The atomic weight of Na is 22.989blabla

The atomic weight of K is 39.0983

So, one 'cup' (or any arbitrary volumetric unit of measurement) of KCl 'should' be about 27% heavier than the same 'cup' of NaCl

You should easily be able to confirm this with a halfway decent scale and a bucket or whatever.

So the combined mass of potassium and chloride is about 27% heavier than sodium chloride.

That means that the same volume of KCl is carrying 27% (or so) less ions in your water stream.

So, it would seem that you need to adjust for such differences if using the NaCl dosing method TC was kind enough to lay out for us all.  http://www.aquaponiclynx.com/salt-for-fish-health     Adding at least about 30% more KCl weight-wise would seem like a good start.

I don't know about the salinity meters you mentioned, but I do know that when using an EC meter, the conductivity, or mobility of different salts varies widely, and is determined by factors such as the 'size' of the ions, the number of ions and the 'charge density' on these particles in solution. For example...the conductivities at 25^OC (77^OF) of 500ppm water based solutions of sodium chloride are 1.02 mS/cm, while potassium chloride is 0.95 mS/cm.

So, a 500ppm solution of potassium chloride has about 27% fewer ions to carry the current than a 500ppm solution of sodium chloride...again, due to the fact that the combined mass of potassium and chloride is 27% heavier than sodium chloride.

At any rate, when targeting a system wide 1ppt chloride salting...just on the basis of weight difference alone it seems like one should add about 30% more (in weight) KCl...

As far as how the different salts relate to applications like intensive salt baths to kill parasites/mitigate bacterial/fungal diseases I haven't a clue. (I have some guesses as to the mechanisms at play, but would not like to air them, lest someone somewhere mistake/misrepresent them for solid info). I would like to know more about it, and probably people like Mathew Farrel or RupertofOz could shed more light and how exactly 3-5ppt salt baths do their magic...