Ok, one more time on KH

[John]

Apologies as I know this topic has been beaten to death but I am getting results that don't match most recommendations I find. 

My issue is one of low KH.   In my 180g indoor aquaponic system i use only pure reverse osmosis water salted to 1-2ppm.    I then add 50%  Hydrated Lime (calcium hydroxide) and 50% Potassium Hydroxide to settle the PH at 6.8.

It seems stable at this PH but drifts downward over a week or 2 which seems a bit faster than I would expect from what I've read. At which point I add a little more of the base solution to bring it back up to 6.8.     Plants are very healthy.  

GH is  125ppm ( or 7 dkh, 7 drops of test solution. ) 

KH is near 0.  (yellow on 1st drop.  but shows 40 on test strip. still low )

PH is 6.8 

TDS is 1430

temp 84F

Nitrate 5ppm

ammonia 0

nitrate 0

Ok. here's the big question:   I have read that I do not want carbonates in my system which is why I do not buffer with Calcium Bi-Carbonate.     KH does not seem to be impacted at all by my 50% each of Hydrated Lime (calcium hydroxide) and 50% Potassium Hydroxide.   So, am I buffering with the wrong materials?      If not, why is my KH not moving at all? 

Trying to follow Nate Storeys' advice along with many other forum posts and web sites.   https://www.youtube.com/watch?v=zP1rUMyklyc but am concerned about 0 KH. 

thanks!

 

[John]

This thread got a whole lot more attn than I expected.    There definitely is a lot more info available online than when I started aquaponics 2 years ago.      Watch Sylvia's video ( link a few replies above. )  She does a nice job of explaining why there is a lot of controversy around carbonates.       I am happy with my water/solution at this point so will just state what I am doing but this is by no means the only answer and experts may think I'm way off.  But since my fish are growing like crazy my plants are healthy, here goes: 

My tap is way too hard to use and has a very high PH.  So in my 180 gallon hobby system I use the following: 

I do top offs w/ pure RO.  About 10 gallons a week. Don't want to increase mineral concentrations by adding mineralized top off. 

System is well established so below is my recipe for partial water changes.  

Start with reverse osmosis water  

Add in some waste water from RO system ( chlorine removed ) to bring up KH some. ( maybe about 10-15% of the total volume ) 

Aquarium salt to 1ppm

Then Potassium Bicarbonate to bring KH to desired level ( Sylvia says 4dkh but mine is a bit lower ) 

I still add in hydrated lime every couple of weeks just because I think the calcium is good for the system. 

Sylvia's Chelated Iron. 

Based on Dr. Nate Storey's videos, I keep my PH between 6.2 and 6.6.   I still see PH dropping enough to add in base every week or so but as a hobbyist, I enjoy tinkering and adding in a bit of base to bring it back up.     I use a digital PH meter just about every day and lose maybe .1 every couple of days but my KH is still between 2-3 so that would probably slow down if I get it to 4-5. 

Thanks for all the replies to this thread everyone.   Much appreciated. 

[Steve R]

To be clear you can not mix carbonates and hydrates you have to pick one or the other and carbontes are vastly more stable easier to use and less expensive and can all be sourced with certified organic products where as hydrates are caustic and can be extremely dangerous to store and use its just not safe or practical for your average aquaponic user when compared to the safety, easy of use and much cheaper cost per year of using carbonates. if you want to grow blue berrys or something where you want to have an exact PH sure hydrates might be your best option but if your not running a grow lab and don't have time to fiddle with your ap system a few times a day its not practical. Most people check on there system every day or 2 for maintain or harvesting and don't want to have to micro manage there system. 

With aquabuffer you could buffer your KH up to 8 or even 10 and let it drift down and only have to rarely dose the system at all to maintain PH or KH because your nitric acid will mostly burn off your KH and not your PH this is a huge reason why its better because it will naturally adjust for increased acid output from spawning or a fish dieing or plants being removed as long as your above 4dkh.  Its vastly more stable and much cheaper per year then dumping lots of hydrates in your system for little stability.

[Vlad Jovanovic]

Steve, to be fair...Yes, you absolutely can utilize both hydroxides as well as carbonates/bicarbonates within the same system. You do not 'have to pick one or the other. And my potassium hydroxide costs me NOTHING. Zero, zilch, not a dime...absolutely FREE. I've blogged and posted about it across a number of different threads when the topic has come up, and how anybody who wants to can make their own. If you are adept enough to bake sugar cookies, you are probably adept enough to make potassium hydroxide. It may not be appealing to everybody, but it may be to certain folks.

Now, that said...I do prefer having some carbonate buffers in my systems. It's just less tinkering. Potassium bicarbonate is a GREAT thing to use to raise KH and pH, especially for 'backyarders', and I have been saying as much for years now...

I agree with you in essence, but using terms like "vastly more stable"..."much cheaper", "dumping lots of hydrates...for little stability" might not be a fair descriptor in every persons set and setting.

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

[Steve R]

Right but practically if some one with out the chemical understanding that you or I have starts mixing and matching its going to end in disaster. Its far easier to make things simple and easy to understand. Hydrates are also infinitely more toxic and potential dangerous.

[Steve R]

Sylvia's great video on carbonates.  http://www.youtube.com/watch?v=AfzyCRcUyYI&list=UUydmHVABaLhwq8...

[Jim Fisk]

Find a good flowing stream and wait till Summer or at least Spring

That advice wasn't just for you Alex.

Alex Veidel said:

Well, it's been like -20F (-28C) outside, so.... no, I haven't really considered that to be a viable option :P Closest water source is my neighbors pond, which currently is thick with ice and is always a tad on the nasty side anyway.

I'm using well water, so there's no fluoride or chlorine.

[Alex Veidel]

Thanks Jim. Spring is here, so I'm back to collecting rainwater :) I was using melted snow until everything thawed out.

Jim Fisk said:

Find a good flowing stream and wait till Summer or at least Spring

That advice wasn't just for you Alex.

Alex Veidel said:

Well, it's been like -20F (-28C) outside, so.... no, I haven't really considered that to be a viable option :P Closest water source is my neighbors pond, which currently is thick with ice and is always a tad on the nasty side anyway.

I'm using well water, so there's no fluoride or chlorine.