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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!

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Your KCl math looks good. In my opinion, azomite is better used in worm tea, or even fish food, than added to the water. Don't be fooled, azomite is just clay, and is interchangeable with some other clays. Most of the volume is just silicon dioxide, and other oxides. It will definately raise your pH. There is a large Aquaponics farm near me that thought it wise to add it. It rallied the pH they took so long to bring down, and they don't use it anymore. It is also high in boron, and they in particular already had very high levels of boron in their source water. It is slow to dissolve, and better suited to soil, IMO.
Your GH is high, but fine if you ask me. Your KH is low, so get some oyster shells in there, or baking soda for a quick source. Easy does it.
The azomite is probably causing the pH rise, but it may also be high carbonates in your source water. Try adjusting 5 gallons of top-water to 7.0, let it stand overnight, and check it 24 hours later to see if it held. It may rebound, and if so you are still adding base each time you refill.

A rise of 0.2 pH isn't really something to worry much about.IMO...

Now Jon...Your kH advice is a good one IMO, and I for the most part share your views on keeping a decent amount of carbonate alkalinity in the system, That's certainly how I'm gonna be keeping things for the foreseeable future... but it's not quite that simple (actually on one level it probably is that simple...but you know me :) ... Ok get this...

Back some time ago Nate Storey and Rupert of Oz were having an Okey Corral moment over the topic of carbonates and carbonate alkalinity as it pertains to bacterial oxidation of NH4. These two gentlemen hold completely divergent opinions on the matter, yet both are EXTREMELY knowledgeable and VERY long time aquapons, and neither one of them are by any stretch of the imagination strangers to the academic side of why/how/what goes on in an AP system. Both have numerous very successful systems running. As you (Jon) may know, Nate runs quite a tight ship. Uses RO water and has expressed his wariness concerning adding carbonates to his system. Most of his alkalinity (pH wise) comes from hydroxides (OH-)  like potassium hydroxide (KOH). By all accounts his kH is probably super low (I guess we could always ask him exactly what his numbers are).

On the other hand, Rupert holds the view that carbonates pose no potential dangers and are an absolute requirement for nitrifyers to live and do their thing...

Now, these two guys are like the Einstein and Tesla of the AP world...so it got me wondering...trying to make heads or tales of what was going on. Everything that I've ever read (studies and whatnot) on the topic dealt almost exclusively with carbonate alkalinity. Which I supposed made sense, since in nature 99.9% of the time alkalinity comes in the form of carbonate alkalinity. That's just the way it is. So, it would make sense that 99.9% of the various studies (wastewater treatment, aquaria, RAS etc)... would deal in that same type of alkalinity. 

But surely some scientists, researchers/investigators somewhere at sometime had to have wondered about non-carbonate derived pH alkalinity and how it relates/affects nitrification? As it turned out I was in luck. I'll try and dig up the study (can't seem to find it at the moment)...to make a long story short...a series of tests showed that nitrification takes place just fine at a decent hydroxide derived pH with almost no carbonate alkalinity. Notice the word almost. Turns out that there is a threshold amount of carbonate alkalinity that needs to be present. If you dip below that threshold amount nitrification will not happen regardless of what the (hydroxide raised) pH is. This amount was really, really quite low, but quite entirely necessary for your bugs to do their thing. 

If I've understood Nate correctly, his main (not sure if it's the only gripe though) gripe with carbonates is that they take away a level of control from the operator, and I'm sure he's right. But, it would appear that some small level of carbonate alkalinity is required to be present in the system for nitrification to successfully occur. By all accounts Nate's systems have a MASSIVE nitrification capacity, yet probably very little carbonate alkalinity is present in his AP systems. 

So Ben's kH is in all likelihood fine for now...Not that I believe raising it would do any harm or anything...Just that it might not be completely necessary. Hell, my water is damned near pretty much liquid rock...

I don't mean to complicate things, but since our systems already take advantage of some 'un-natural' situations (from artificial lights, to artificial heat blablabla)...in all liklihood there may be benefits to some not-found-normally-not nature pH situations to take advantage of as well...like hydroxides...of course you'd probably have to check and adjust your pH daily since there would be little if any buffering capacity in your water as a safety net against a pH related bio-fiter crash. But doing things that way would seem to give you an awesome control in keeping a very tight/exact (low plant loving) pH at all times. (And long as you didn't get lazy about it...in which case it'd probably be a disaster 

Agreed Vlad. And I am still learning/understanding the science. Is this the video that you are referring to between Nate and Rupe?

http://community.theaquaponicsource.com/video/bringing-up-ph-levels...

If so, it's what started my own tangeant of research. At first, I took Nates word for it, and why not? Then when Rupe offered new insight (I miss Rupe on the site, but I get why he's gone) So I did my own searching. Now, I'm sure life can eke out an existence in any special circumstance, but the natural order of things in the larger factions of the nitrifying world, need carbonates. Not for alkalinity, but for the carbon. Now, I'm no pro here, but literally everything I read agreed to that statement. Perhaps they can also survive on decaying carbon mulm in the water, or CO2 as someone posted in Nate's vid (which is a tiny, delicate, slow-breeding rarity, not the norm), but carbonates drive the machine. I agree that nitrifying bacteria are fine in low levels of KH, but their existence is dependent, as I understand it, on the presence of KH to build more bodies. If the demand for more bacteria goes up, and there is no KH available, then the bacteria population is compromised? That's my understanding.

Now, I also respect Ryan Chatterson of Aquatic Eco Systems, and Dr Ebeling (co-author of the fish farmers bible called "recirculating aquaculture"). I had the treat of listening to Ryan talk, and Ebeling was in the audience. Ryan pitched guidelines for water chemistry, amd the KH was from min 40 on up (I can't remember, probably a couple hundred). Agreed, as that is pretty common textbook advice, but Ryan then said he runs his at 40, the minimum count. Ebeling groaned, clearly on Rupert's side of fence. I would assume Nate also runs his KH low, but probably not lower than 40. So, with Ben's KH of 50, I'd say it's safe to say that is low, but ok. I have no difficulty keeping pH smooth with KH over 100, and I have personally had a system teeter on crash from low KH (literally less than 17 ppm, as the first drop of reagent changed the color completely).

I'll invite Nate over, and Ryan. Sorry Rupe.

Thanks for all the feedback. I just purchased the book by Dr. Ebeling, "Recirculating Aquaculture". Hopefully after reading that and doing some more research I can have a better understanding of this whole carbonates topic. From that exchange between Rupe and Nate I actually find myself agreeing more with Rupe, or at least the 50/50 approach; at least until I do some research for myself and obtain a more thorough understanding. 

Now back to my office system, the top-water I have been adding is very high pH, about 8.2 or a little higher. So it more than likely has high carbonates. could be causing the pH to rise. I just recently purchased an RO water filtration system for my house and aquaponic systems so that will be my new source of top-water. It has a pH of 5.8. So I will see if the low pH and RO water will begin to make a difference in the pH swing as well as get some KHCO3 in there to try and help bump up the KH a little bit. I am an advocate of daily water pH testing and very close overall water monitoring, so hopefully that will prove beneficial to help me get to the bottom of this. Anyway, I post updates as they come along. 

Yup, that's the one. I wanted to post the study then, but figured I'd stay out of the clash of the titans :) 

Yup, agreed (in my world...the way my limited understanding can grasp  it...) Nitrifiers need a carbon source and carbonate alkalinity seems like as good a meal as any. This over reliance on carbonate alkalinity may seem silly to to people like Nate and Ryan, but they are on a 'completely different level'...Rocket Scientists, if you will. 

I have no problems keeping a pH within my personal target range while dealing with the carbonates at the same time (at least thus far). I've worked hard to acquire that 'zone of comfort' that being able to so so affords me, and I'm not about to shake those foundations anytime soon :) (Man, that sounds so damned christian)...And besides, I'm kinda lazy, and like the 'safety net' that carbonates provide for now. (Like I said, silly reasons too be sure)...

Yeah, I miss Rupert's insights as well. He sure was a 'straight shooter' when it came to fish biology, plant physiology and water chemistry...probably held more insights into those topics than the two of us clowns combined...

Cool deal Benjamin. Keep us all posted (as tedious as it might be for you at times). Play with the RO water...See what kH  readings are in the system...kH readings of the RO water...you have a great learning opportunity in front of you. If you're up for it, grab some KOH to raise pH with as well (instead of just a CO3 source). And since your a fan of daily water quality testing...experiment a bit. JUST MAKE SURE TO TAKE GOOD NOTES.  And please let us know what you've observed :)



Benjamin said:

Thanks for all the feedback. I just purchased the book by Dr. Ebeling, "Recirculating Aquaculture". Hopefully after reading that and doing some more research I can have a better understanding of this whole carbonates topic. From that exchange between Rupe and Nate I actually find myself agreeing more with Rupe, or at least the 50/50 approach; at least until I do some research for myself and obtain a more thorough understanding. 

Now back to my office system, the top-water I have been adding is very high pH, about 8.2 or a little higher. So it more than likely has high carbonates. could be causing the pH to rise. I just recently purchased an RO water filtration system for my house and aquaponic systems so that will be my new source of top-water. It has a pH of 5.8. So I will see if the low pH and RO water will begin to make a difference in the pH swing as well as get some KHCO3 in there to try and help bump up the KH a little bit. I am an advocate of daily water pH testing and very close overall water monitoring, so hopefully that will prove beneficial to help me get to the bottom of this. Anyway, I post updates as they come along. 

Hey Vlad, I have another question for you and it's related to previous posts in this discussion so I figured I would ask it in here. I did a water test of my main system last night (the one that had the retarded pepper plants that I took out) and I tested the KH and GH of that system for the first time. I was pretty shocked to find that my GH was completly off the charts high (it took 42 drops to change the color and even then it was a really weird dark color that wasn't really what it was supposed to change to and I would guestimate that around 800 ppm GH according to the test kits chart) and when I tested my KH it barely registered anything at all! (took one drop to change the color so according to the test kit that would put it anywhere between 0-17.9 ppm). Do you have any insight as to why this might be??? Now please correct me if I'm wrong but it is my understanding that GH is basically a measure of Ca and Mg in the water and almost always that Ca is in the form of CaHCO3. If that was the case then the GH and the KH should usually be fairly consistent with one another. Is it possible that though my top water has both a high GH and KH  the nitrification process is using the carbonate alkalinity faster than it is being added in with my top water? Also, the buffer that I have been using since I started the system about 6 months ago has been exclusively KOH just because that is all I have had available to me without ordering online. Your quote from an earlier post said,"for every 1mg of NH4 they convert to NO3 they use up  around 8mg of carbonate alkalinity (and about 4.5mg of O2)." In my 80 gal system about 300mg = 1 ppm. would that mean (300 / 8 which is 37.5) for every 37.5mg of NH4 that's converted to NO3 1ppm of carbonate alkalinity is used? Hope you can help :)

Ben, I know you directed the question to Vlad, but in the meantime let me just say thanks for following thru and testing. My teetering system has exactly the same issue you are having, suitable GH, and zero KH, and I came to the same conclusion, that the carbonates have been consumed by nitrifying bacteria. Soaking 20 lbs of coral wasn't enough to get a reading after 2 weeks (even with a pH of 6.0), so I added a 1 lb of sodium bicarbonate. I now test 40 ppm, and I am moving my coral bag to the inflow stream of the FT (lowest pH in the system).

Since you have only been using KOH, you are not adding any carbonates, and it is possible your top-up water may be hard and at the same time have low or no alkalinity. Rare, but not impossible. I know my water has very high manganese, and all my older systems have extremely high GH, probably from manganese/iron. I may have to replace some of my older water with rainwater and supplement with carbonates of some kind to rejuvenate things.

I found this, somewhere on line, "More than 85% of American homes have hard water.[45] The softest waters occur in parts of the New England, South Atlantic-Gulf, Pacific Northwest, and Hawaii regions. Moderately hard waters are common in many of the rivers of the Tennessee, Great Lakes, and Alaska regions. Hard and very hard waters are found in some of the streams in most of the regions throughout the country. The hardest waters (greater than 1,000 ppm) are in streams in Texas, New Mexico, Kansas, Arizona, and southern California.[46]"
[edit]

So, your figure of 800 ppm is not unheard of, even in nature. One of my tanks has 630 ppm, yet moderately low carbonates. Here's another cut and paste... "Although strontium, aluminum, barium, iron, manganese, and zinc also cause hardness in water, they are not usually present in large enough concentrations to contribute significantly to total hardness."
It's these variable water sources that make me cringe when experts make statements like 'avoid buffering with carbonates' or 'there is never a need to add acid, just be patient' or 'rainwater is preferable to well-water' or 'RO should be used' yada yada. What works for Colorado well water may not be suitable for Cali, or Serbia, or wherever, and even your regular water source will fluctuate with the seasons. Better to understand the principles, than make blanket statements.

Thanks Jon, I am not familiar with using coral. Is it just used as a way to have a slow and steady release of bicarbonates in the water? I will definitely add some sodium bicarbonate tonight just to get the KH up and I just received my KHCO3 that I ordered online so I'm hoping buffering with that will keep my KH at adequate levels. The reason I am concerned about my GH is because if the hardness is primarily from CaHCO3 I was worried that the Ca levels might be too high in the system and that could impede the uptake of over key nutrient, primarily K. Do you know at what levels of Ca this occurs? 

Ben, out of curiosity, what are your baseline numbers out of the tap? That would be an good place to start. 

Coral, oyster shells, limestone, marble, chalk, all sources of CaCO3, amd when put in a bag I can yank it if KH gets too high.

I don't know at what point K is compromised due to Ca levels, and I think it's more of a ratio of Ca to Mg to K, than it is total Ca quantity. I'll look into it later. Or hopefully Vlad knows. I might have to track Rupe down in Oz.

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