Has anyone used Kalkwasser in aquaponics? It is designed specifically for use in marine applications and according to the label is is pure calcium hydroxide. calcium hydroxide is an ideal compound for raising ph due to the added benefit of raising calcium levels which are commonly deficient in systems due to the low level in fish feed. If anyone has used this stuff did you record any data on how much you added for a and how much it affected your specific system? Any input would be appreciated!

Tags: alkalinity, buffer, calcium, hydrated, hydroxide, kalkwasser, lime, ph, pickling

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Kalkwasser, packaged and sold the way that it is, seems like a really expensive way to buffer with calcium hydroxide [Ca(OH)2] ...4.4lbs for $31...I'm pretty sure you can get a 25lb bag of calcium hydroxide for less than $10 bucks...or less

Calcium hydroxide is also called slaked lime, hydrated lime, pickling lime, builders lime...it's all just CaOH2. And it's all pretty much made the same way...everywhere...for thousands of years... You can find it at any tractor supply store, Home Depot, garden store, most hardware stores etc...I'm sure the Kalkwasser (which is the German word for "lime water") product will work just fine as well...just seems like a totally ridiculous price to pay for some builders lime      my two cents...

Okay thanks for the info, I appreciate it! I was aware of all the lime products are also calcium hydroxide I just wasn't sure if they met the same purity levels that the Kalkwasser does. I read that Kalkwasser can even be used at low levels in potable water. I just assumed that especially the builders lime wouldn't be of the same quality or pureness or that it might have some filler in it due to the fact that it's not coming in contact with fish or potable water. I guess the pickling lime is used for food preservation so I can fairly confidently assume that it would be safe for aquaponcis as well. I guess I just get a little paranoid when it comes to adding anything to my aquaponics system. 

Speaking of adding something to an aquaponics system, do you have any experience with a product called Azomite? It's "A to Z of Minerals Including Trace Elements" and used in the agriculture industry. What are your thoughts, if any, on the use of this in aquaponics?

Thanks again!

Nope, no thoughts...other than it's chemical make up would probably raise your waters pH...Which could be good, could be bad, and probably depends on how (and how much) you use it...

You can get all the trace elements you need by using some sea water (since you live nearby)...or pure sea salt. Just watch the anti-caking additives if the salt contains any, that is. I know most folks here just say "don't use any salt that has anti-caking agents", and that's probably the safest route to go...and requires the least information on the part of the AP system operator, but the truth is some anti caking agents are perfectly OK, while others might not be...Some common NOT ok caking agents are sodium ferrocyanide, and potassium ferrocianide (these will often be listed as E535, or E536 respectively, and wont degrade into cyanide or hydrogen cyanide gas when consumed by humans, but an AP setting might be a bit different, so they should probably be avoided). Some totally cool anti-caking agents commonly used in NaCl and KCl salts are calcium carbonate or magnesium carbonate...It's pretty hard to beat seawater for TE's (not to mention Mg and K) IMO...Especially for the price...

If you have high pH "hard" (high kH) source water, you can get yourself a potassium based buffer like potassium bicarbonate (KHCO3) from a wine making shop, or online...

I thought that KHCO3 is used to raise your pH? General Hydroponics "pH Up" base solution is a potassium hydroxide and potassium carbonate mixture. Perhaps I don't have a thorough understanding of pH and alkalinity. It is my understanding that alkalinity is the buffering capacity of a body of water. So while you would be increasing the alkalinity by adding the potassium carbonate, wouldn't you also be increasing the pH? Thank you for your detailed responses, I am still fairly new, compared to some, in aquaponics and am always trying to increase my knowledge. 

Yup...KHCO3 is used to raise pH...just like CaHCO3 will also raise your pH every time you top up (calcium bicarbonate is just what calcium carbonate is called when it's dissolved in water)... 

Yeah, alkalinity just refers to your waters ability to neutralize (or buffer) acids...your bacteria produce acids just by living and oxidizing NH4 to NO3...On this forum people seem to like to use the phrase "buffering capacity". So, Buffering capacity = Alkalinity. Interchangable terms here on the forum...

This alkalinity will eventually get 'used up' by your bacteria...remember for every 1mg of NH4 they convert to NO3 they use up  around 8mg of carbonate alkalinity (and about 4.5mg of O2). When the buffering capacity (alkalinity) starts go get used up, you'll notice your waters pH start to drop...and if you don't intervene to 'buffer' it back up, it will continue to fall and your bacterial colony will crash and burn (pH 5.5 or below...or thereabouts).

This alkalinity usually comes in the form of CaCO3, but it's amount is location dependent (though if you have high pH water it's a pretty good bet that it is carbonate alkalinity. Just as if you have "hard" water ( high gH...which is just a measure of Ca and Mg in the water...you can bet your booty 9 times out of 10 that most of that Ca comes in the form of...yup, you guess it Calcium carbonate)...(such is the case in the natural world... alkalinity in nature is usually carbonate alkalinity)...

Realistically, if this is your waters situation...you shouldn't need to make any additions for the calcium that you originally mentioned. See, any time you, or the bacteria 'add' acid to the water you the reaction releases plant usable Ca2+ from the CaCO3. So, Ca is hardly ever a problem in AP, except in the sense that there is often too much of it...which has the very real potential mess with the K (potassium) and to a lesser extent Mg uptake of plants. As all the base metal cations are antagonistic in relation too one another and coexist in a relationship of balance...(except iron, an excess of Fe doesn't seem to negatively impact the uptake of any other plant essential elements...iron is funky that way...though making unnecessary additions of Fe, in unnecessary quantities does seem to negatively impact the pocketbook...)

In new-ish systems K seems to be the limiting factor...Hence the KHCO3 buffer (only when it becomes necessary to raise pH of course). A good idea is to alternate between a K buffer and a Ca buffer and throw in a cylce of Mg buffer (dolomitic lime) here and there, but sparser than the other two buffers. Your Ca buffer can just be your top up water (if it's full of CaCO3)...For some people, their system and source water parameters work out so that just by topping up, they are providing the added alkalinity (buffering). While others need stronger alkaline additions of some sort hydroxides or carbonates (a 'potassium' buffering agent is a real good idea in that case IMO)...

My water does happen to be on the high pH side(around 8.0). So based on what you just explained, it's not very likely that I will need to buffer with CACO3 very often or ever. If a daily topping off of my system counters the acidic effect of the nitrification process and keeps my pH at the desired level (in my case it's 6.8) and adds enough Ca,  how would I ever use the KHCO3 to supplement K in the system?

Vlad Jovanovic said:

Yup...KHCO3 is used to raise pH...just like CaHCO3 will also raise your pH every time you top up (calcium bicarbonate is just what calcium carbonate is called when it's dissolved in water)... 

Yeah, alkalinity just refers to your waters ability to neutralize (or buffer) acids...your bacteria produce acids just by living and oxidizing NH4 to NO3...On this forum people seem to like to use the phrase "buffering capacity". So, Buffering capacity = Alkalinity. Interchangable terms here on the forum...

This alkalinity will eventually get 'used up' by your bacteria...remember for every 1mg of NH4 they convert to NO3 they use up  around 8mg of carbonate alkalinity (and about 4.5mg of O2). When the buffering capacity (alkalinity) starts go get used up, you'll notice your waters pH start to drop...and if you don't intervene to 'buffer' it back up, it will continue to fall and your bacterial colony will crash and burn (pH 5.5 or below...or thereabouts).

This alkalinity usually comes in the form of CaCO3, but it's amount is location dependent (though if you have high pH water it's a pretty good bet that it is carbonate alkalinity. Just as if you have "hard" water ( high gH...which is just a measure of Ca and Mg in the water...you can bet your booty 9 times out of 10 that most of that Ca comes in the form of...yup, you guess it Calcium carbonate)...(such is the case in the natural world... alkalinity in nature is usually carbonate alkalinity)...

Realistically, if this is your waters situation...you shouldn't need to make any additions for the calcium that you originally mentioned. See, any time you, or the bacteria 'add' acid to the water you the reaction releases plant usable Ca2+ from the CaCO3. So, Ca is hardly ever a problem in AP, except in the sense that there is often too much of it...which has the very real potential mess with the K (potassium) and to a lesser extent Mg uptake of plants. As all the base metal cations are antagonistic in relation too one another and coexist in a relationship of balance...(except iron, an excess of Fe doesn't seem to negatively impact the uptake of any other plant essential elements...iron is funky that way...though making unnecessary additions of Fe, in unnecessary quantities does seem to negatively impact the pocketbook...)

In new-ish systems K seems to be the limiting factor...Hence the KHCO3 buffer (only when it becomes necessary to raise pH of course). A good idea is to alternate between a K buffer and a Ca buffer and throw in a cylce of Mg buffer (dolomitic lime) here and there, but sparser than the other two buffers. Your Ca buffer can just be your top up water (if it's full of CaCO3)...For some people, their system and source water parameters work out so that just by topping up, they are providing the added alkalinity (buffering). While others need stronger alkaline additions of some sort hydroxides or carbonates (a 'potassium' buffering agent is a real good idea in that case IMO)...

Well, see if it works out that way first ...

If it does, there are other ways to introduce K into a system if you need to. Watch your plants and see what they tell you. Document and take note of any signs of deficiencies...Really though, if your feeding your fish a decent quality feed, and your systems been running a bit and had time to mature, and your pH is under control...You probably wont have much to worry about as far as that goes. 

okay, will do haha. What would be those other ways though of introducing K? My system is not mature yet and is still showing some deficiencies. pH is sitting at 6.8, ammonia and nitrites are showing 0 ppm and nitrates are about 80 ppm. I have a pepper plant that looks like death and some lettuce right next to it that looks great. Thought that could be a K deficiency? Maybe the pepper plant requires more than the lettuce? I attached a picture of both. 

Well, KCl is a good soothing Cl tonic for the fish...with the added benefit of K without raising alkalinity. Or seawater (many trace elements there and a good deal of Magnesium too). Don't get too caught up worrying about chloride salinity...Many folks salt there systems with NaCl (for the fish) to the tune of about 1ppt (yup that's parts per thousand) with no ill effects whatsoever. I have chose to use KCl instead...Jon Parr is going with a half and half combo. So far things are great.

Maxi Crop/Seasol/Kelpak would help a bit too. K deficiencies usually start off as a bit of yellowing around the very edge of the leaf, then progresses to a necrotic whitish-brown, while little yellow "spots" then appear over the leaf surface. These spots soon turn the same dead whitish-brown...In which case it's usually too late to really do much IMO. Leaves in peppers may curl upward and get 'crinkly'...

Yeah, different plants may have drastically different essential element requirements...hot peppers aren't so bad though. They're still lightweights compared to zucchini, cukes, toms, sweet peppers...(pretty much in that order)...

I think I will give the KCL a shot then and see how it goes. Do you recommend any starting point for the initial amount to add? So you're saying that the sweet peppers are the highest demanding of the bunch? I shouldn't have been so vague in my last comment, hahaha, because that disgusting looking plant is a sweet pepper plant; not a hot pepper. I decided it was past the point of no return and took it out.

Toms and sweet peppers are a bit less demanding than the squash and cukes...still nothing to sneeze at though...

If you're asking what I would do, I'd first read this link http://www.aquaponiclynx.com/salt-for-fish-health     to get an idea of weights and measures. Then I'd get some pure dehydrated sea water (sea salt, solar salt or whatever it's called in your area) and some KCl.

I would then add each to the tune of 0.25ppt. 

KCL at 0.25ppt

NaCl at 0.25ppt

Or, I would be content with just growing leafy greens real well for about a year...but where's the fun in that?

Ben, to answer your question of how to take advantage of the potassium from KHCO3 when your system is already a high pH, simply use enough acid to keep it in range. The KHCO3 is still in there when you add it, it just takes more acid to keep the balance right. That being said, I don't use KHCO3 because KCL is cheap, available, easy, and doesn't alter pH. I do recommend salting to a total 1/2 - 1 ppt using a mix like Vlad mentioned, for the sake of fish and plants.

However, I don't think K def is your problem. I think it's Ca def. You really do have to check GH and KH. While high pH does usually indicate hard water, it is not always so. It is possible to have soft water with a high pH. For most of the nation, general hardness is composed mostlyof, if not entirely of carbonate hardness, but it may not be the case for you. And, to further mess things up, water source hardness changes with the seasons. I have hard water, typically, with decent CaCO3, but a recent new system was (still is) teetering on acid crash after cycling. My GH is perfect, and my KH was zero. Perhaps the rapid population growth of bacteria consumed it, or perhaps it was oddly in short solution when I filled the system. It was, BTW, filled entirely with 8.8 well water, and the KH reading of zero was before the rains came (I didn't check any hardness readings before acid crash was looming, so I don't know what the original hardness of fill water was). I'm sure the rain isn't helping any, but I'm finally reading some KH after hanging a big bag of coral sand and some dolomitic lime.

Anyway, take a gander at this vid, and see if that doesn't resemble your peppers. http://www.youtube.com/watch?v=nwpYuP1as-M

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