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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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IDK Jon, I mean it could very well be that some Ca is lacking, but...when I was inducing various deficiencies to get a first hand looksy at seemed like Ca def resulted in more of a bumpy-ness and 'crinkly' leaves....I'm looking at the leaf margins in the pic and seeing tell tale (to me) chlorotic and even some necrotic margins...and the chlorotic spotting over the broad surface of the leaf...and the way that one leaf bottom left, has totally curled upwards like a cup. All of those things look indicative to K def to me.

Hey remember that one goofy hot pepper plant that was all fucked up every which way...the Quasi-Motto one from the "duel root-zone" write up? It was in the same reservoir with all the others and the other 4 were fine? But that one plant was just a mess...Kinda like Ben's...It's always a good idea to plant a bit extra and weed out the inferior plants, so if you get one goofy out of three of the same cultivar that is messed up... you don't go batty trying to figure out what deficiency you may or may not have...The way you might if you only planted one, and it turned out to be just a genetically defective plant (happens)...Is that the only pepper you had in there, or were there more, and they were all like that?

Good point. Lock that pepper in the bell tower

Plus when you plant extra's, when you weed them out, it gives you an opportunity to check out the roots and root heck for signs of things like pythium, collar rot etc...catching that kind of stuff early in the system means a lot!

Oh yeah, if you do drop the pH of the KHCO3 solution, it'd be a good idea to mix up the KHCO3 in de-mineralized water or rain water. Then add the HCl to drop pH. That way you can keep the dissociation nice and tight. KHCO3 plus HCl should dissociate into mostly KCl and a bit of CO2...If you use tap water it'll just complicate the acid/base reaction with carbonates (I mean you can do it that way too, but demi or rain water/melted snow would be much more preferable)...Then just add that water to your system...

The retarded pepper plant was not alone. I had two others in the grow bed with it and they too were showing to same signs just at a different severity. I greatly appreciate all the extremely insightful feedback from you guys, it is becoming more and more clear to me that 1. I wish I would have majored in chemistry, botany and marine biology in college & 2. my understanding of aquaponics is entirely inferior to both of yours. That being said, for almost every answer I get, it leaves me with about a half a dozen new questions. So I apologize if I continue to bore and pester you with my mundane questions. Here are a few that I have after reading those responses;

- In an aquaponics system what would be good levels for GH & KH? who makes a good test kit?

- Since really low KH levels can cause extreme fluctuations in pH, can really high KH levels impede ones ability to alter pH?

- Jon you had said to maintain pH while adding KHCO3 one should offset it by adding acid. Is it okay to add the KHCO3 and acid in the same bucket with your top off water?

- In one of Murray Hallam's videos he recommends not adding a potassium buffer any time close to adding a calcium buffer. I had consulted with Dr. Wilson Lennard about this and he assured me that he mixes both buffers in the same bucket before adding them to his systems with no problem. Any opinion on this?

- How often do you recommend salting you system? and at what point do the Na levels have to be before they become detrimental the the fish and plants?

1) Tetra makes a decent kit, but I'm sure there are others.

2) Yep. kH is just a measure of carbonate hardness. Most of that comes from calcium carbonate (or more correctly calcium bicarbonate...same shit bassically, but that's what calcium carbonate is called when it's dissolved in water). So, since calcium carbonate is a base, a very high level will be able to neutralize a lot of acid...hence impeding your ability to alter pH downward. You add acid and the pH goes down at first...then creeps back up as the acid is neutralized and there's still a bunch of carbonates present.

3) See my above post...It should absolutely IMO be mixed up in the same bucket...with rain/distilled or otherwise mineral free water. Then use that mixture to top off with.

4) Total bulloks IMO. There should be nothing wrong at all with "adding a potassium buffer any time close to adding a calcium buffer" Maybe Mr. Hallam is confusing potassium with phosphorous...Which should most definitely not be mixed with any form of calcium.

5). Well now that's a trickier one and most subject to set/setting and preferences (the "how often part"). Different fish have different tolerances to salinity. Different plants have different tolerances to salinity (folks have been reporting that strawberries are particularly sensitive...which jives with the literature...but all should be well at around 1ppt...with folks reporting lettuce and greens doing fine at WAY higher 3ppt or more even...Ask Mathew Ferrell for the details on that one as my memory is foggy on the exact numbers...Just know that they were 'way high' in the tests that one of his acquaintances successfully ran)...

Anyway, unless you have the equipment to measure such things...salinity (which is a measure of chlorides/sulfates basically...the Na is not the problem)...It's gonna come down to a bit of voodoo-mojo-intelligent-guestamation...Just don't over do it. Maybe once or twice a year would be good...And see to time the KCl-NaCl additions with when your heavy fruit bearing plants would need it most (if you have any...tom's cukes zucchini etc)...that would be a smart time for such additions...

I use General Hydroponics pH down to lower my pH, which is a phosphoric acid solution. So if I understand you correctly it is okay to mix this with KHCO3 or KOH but it can't be mixed with any calcium solution?

Phosphorous in the more common form of phosphates is to be avoided mixing with calcium...I'd not use that product for a number of other reasons though. I'm not telling you not to use it, just that I wouldn't. For one, citric acid is anti-bacterial, and you are trying to establish a bacterial colony. 2) Excess phosphates (which is what the phosphoric acid would eventually dissociate to) is a great way to induce an algae bloom. If your fish are being fed they are creating PLENTY of phosphates. 3) Mono-ammonium phosphate...(again, more phosphates) and extra ammonia. If you've properly stocked your system, why add more ammonia?...On the other hand, HCl releases a bit of fish helpful chloride ions when it dissociates. I'm not saying "don't use the stuff", just that it doesn't really seem like the most AP appropriate acid with which to lower pH with. (Especially when HCl is cheaper and more appropriate for the application. I used to use phosphoric acid in hydro applications's a great way to add a phosphate 'reagent' while lowering pH at the same time, but again fish effluent contains plenty enough of those...and in a 'sterile' hydro environment an anti bacterial agent is a good thing)...But, don't worry about the calcium thing with a phosphoric acid...just with phosphates.

What would you recommend for a good HCL? can I use just regular swimming pool Muriatic acid? I used to clean swimming pools in high school and that wasn't exactly my favorite chemical to use.

Yeah it's pretty strong stuff. No strong acid is real "fun" to work with though...The stuff I have access to (available at every corner store here) is a 16-18% HCL solution. But, yeah any Muriatic/pool/hydrochloric/acid...spirit of salts...whatever HCL is called in your neck of the woods should be fine (so long as the ingredients are just HCl and water...which they should be)...

Okay I think I have some pool muriatic acid I had used for cleaning some concrete a while back, I'll just have to confirm that there's nothing else added in it. 

This is another random question that I just ran in to after testing my GH and KH. So in my small office system which has been up and running for around 3 months (with very exceptional plant growth in my opinion considering how young the system is) I have quite a conundrum that I thought you could possibly help with. My pH has slowly been on the rise for about the last 3 weeks. In that time it has gone from 7.0 to 7.2. It seems to be holding pretty steady at 7.2 now though. There is no ammonia, no nitrites and the nitrates are around 80 PPM. My first thought was that maybe there is an anaerobic zone in the system which could cause a slow increase in pH but that to me seems nearly impossible  due to the infancy of the system, the minimal fish waste entering the grow bed, the small root systems from my young pepper plant and the flow rate going through the system is very fast. (F&D GB on about a 4 min cycle) After ruling out that option I thought maybe my KH is so off the charts high that it is preventing the nitrification process from lowering the pH but if that was the case I don't think the pH would be increasing at all. My fill water has a high pH but I have put acid in to offset it so it goes in at about pH neutral. (phosphoric acid which I will now be changing over to HCL per your recommendation :) One thing I should note is that as an experiment when I originally cycled this system I had added a couple teaspoons of azomite. Perhaps this could be the culprit, but this very very slow increase seems to be rather new.  I got a test kit to test GH & KH and got some interesting readings today. GH: about 500ppm KH: about 50ppm  Any thoughts??????

I'm terrible at these damn conversions so I just wanted to double check my math with you. If I am adding KCL to the tune of .25 PPT in a 13 gallon system I am getting 12.3 grams. Is that correct???

13 gal = 108.42 lbs

108.42 lbs = 49.1785 kg

so to add KCL levels at 1ppt I would add 49.1785 g

49.1785 g x .25 = 12.294625 g

Vlad Jovanovic said:

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     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?

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