Anyone Used Potassium Carbonate As A 'ph Neutral' Kh Buffer?

[BubblesLotsOfBubbles]

I ask because the experiment I tried with it sent my pH through the roof and I'm not really sure how a change in pH of this magnitude happened...
 
It turns out my tap water is very variable and is often very soft and I've seen pH crashes so wanted about 4 or 5°KH for stability as a starting point. I had earlier played around with baking soda but found it made my pH rise too high. I read (  http/www.theaquariumwiki.com/KH  ) potassium carbonate will raise KH but not pH. So here is what I did
 
5 litres of fresh tap water was measured for TDS (043ppm) and pH (6.8-6.8) KH (changed at 1 drop API test kit IIRC this is less than one degree KH - lost the paperwork! so 1° KH ) GH changed at two drops (so same again IIRC 2°GH).
 
This was aerated overnight.
 
The following day the pH had risen to a definate pH 6.8.
 
I added various amounts of potassium carbonate and finally deduced 'If I add X amount my KH will be 5 degrees', which when undertaken, did have the forecast effect as the KH test pointed to 5°KH (ie colour changed with addition of five drops test solution). Due dilligence had me re-check my pH and I was quite shocked to see the pH had moved from 6.8 to over 8.2 - maybe drastically over as the purple colour of the test kit was seriously purple! And being a log scale that's a lot more.
 
To put this into context when my tap water maxes out my GH & KH test kit ( full dosage of 12 drops of each GH and KH solutions to either get no colour change or colour change on the very last drop) and is aerated to pH stabilisation, that stabilisation happens at pH 8.2 (from an initial 7.2-7.6). In this instance of using a 'pH neutral buffer' to get only 5°KH the pH has moved from 6.8 to way above 8.2. So for my 'hard' tap water of 12°KH/12°GH the pH is 8.2 while the 'pH neutral' buffer of only 5°KH is way above pH 8.2 from a lot lower starting point pH. HUH?  So what the aquarium wiki says doesn't add up, re: - "Potassium carbonate (K2CO3) A known food additive. This adds carbonate without raising pH".
 
I emailed the seller of the potassium carbonate to ask if there may have been a mix up. They replied with some general info but here is the key line: "However if there is any acids present in the water, then the K2CO3 will react to form Potassium bicarbonate (KHCO3) which produces extra H+ ions and so the pH will rise".
 
Has anybody played around with this stuff enough to say "Yeah what you have seen will typically happen". If so the aquariumwiki is quite misleading. Or maybe I haven't been given potassium carbonate.
 
I find this all quite peculiar!
 
 

 

[TwoTankAmin]

Increasing H+ lowers pH not raises it.
 
KH is what holds pH steady in the face of added acids. Higher pH waters typically have higher KH.
 
Calcium carbonate and potassium carbonate are used to raise pH.
 
Why are you trying to change your tap water chemistry? This is a way more complex process than you probably realize already. Start by reading here to get a feel for with what you are dealing: http/fins.actwin.com/mirror/begin-chem.html#altering

 

[BubblesLotsOfBubbles]

Increasing H+ lowers pH not raises it.
 
KH is what holds pH steady in the face of added acids. Higher pH waters typically have higher KH.
 
Calcium carbonate and potassium carbonate are used to raise pH.
 
Why are you trying to change your tap water chemistry? This is a way more complex process than you probably realize already. Start by reading here to get a feel for with what you are dealing: http/fins.actwin.com/mirror/begin-chem.html#altering

 
Thanks but I said all that didn't I, (apart from the seller's words that is) EDIT: Not being picky just making sure we are agreeing on the same points? But you do say potassium carbonate is used to raise pH so you are agreeing with me that what I saw was typical and the Wiki is incorrect?  And also disagreeing with what the seller said?
 
In reply to your question, I am trying to change my water as I said because its very variable (Eg water of 19th Feb was TDS 043ppm, 1° KH, 2° GH, pH 6.8 and when tested on 21st in the tank it was pH 6 or under. Todays water was TDS 288ppm, 10°KH, 12° GH, pH 8 which will likely move to 8.2 or higher in the tank). I've had 3 pH crashes from using it when its soft and I've read widely fish don't like a change of even pH 0.2 over a 24 hour period so my water ranging from 6.8 to 8.2 isn't good.  When its hard it stabilizes at a pH of around 8.2 which is also higher than I'd like. However most of the time its very soft, so with the 'soft' water being most prevelent as I said I wanted to simply add some KH for stability (aiming for 5 degrees) but not having the pH going as high as pH 8 and over. I was wanting a pH around 7. The wiki's advice regarding potassium carbonate seemed the ideal solution but actually turned out to be way way out from what I have seen, and wanted to know if this was typical or not.
 
Changing my own tap water is the best solution for me.

 

[BubblesLotsOfBubbles]

My next experiment is going to be with dolomite lime for Ca. Mg for the redox and osmoregulation and pH stability.

 

[TwoTankAmin]

When you add chemicals to a tank, it raises the TDS.
 
Did you outgas your tap water before testing it?
 
My guess is your calcs may be off and the result is the carbonate you added raised the KH more than your realized which buffered up the pH.
 
Different fish can handle different levels of pH and TDS changes better than others. And the changes in pH are rarely the issue it is the change in the cinductivity/TDS that are the concern. I have personally dropped the pH in a tank or two by 1.0 inside of 5 minutes and the fish did n;t blink. But they were wild caught fish from acid waters. I have cut the TDS in half with a single water change to ftrigger spawning, and the fish didn't blink.
 
What is more of an issue is when one raise the conductivity/TDS for most fish, except those adapted to living in hard water. They do not like big drops.
 
Where the Wiki site is wrong is that you cannot raise KH a lot and not have the pH rise as well. And you for sure cannot do it without raising the TDS, I dose muriatic acid into a tank to lower the pH. To destroy some tap KH and to prevent the addition of the acid from raising the TDS, I use 50% ro/di water mixed with my tap. It also took me about 10 years in the hobby before I was even willing to try this.
 
My point in sending you to that link was so you would read about the parameters but, most importantly would read this:

 
Note: GH, KH and pH form the Bermuda's Triangle of water chemistry. Although the three properties are distinct, they all interact with each other to varying degrees, making it difficult to adjust one without impacting the other. That is one reason why beginning aquarists are advised NOT to tamper with these parameters unless absolutely necessary. As an example, ``hard'' water frequently often comes from limestone aquifers. Limestone contains calcium carbonate, which when dissolved in water increases both the GH (from calcium) and KH (from carbonate) components. Increasing the KH component also usually increases pH as well. Conceptually, the KH acts as a ``sponge'' absorbing the acid present in the water, raising the water's pH.

from http/fins.actwin.com/mirror/begin-chem.html

 

[BubblesLotsOfBubbles]

Thanks for your reply. Don't worry I have read a fair bit about water chemistry and even the Bermuda Triangle references. I read a lot  of the interealtionships. What I didn't read a lot of was the wiki idea about potassium carbonate. I therefore thought I had found a little gold nuget during my research that could obviate the 'Triangle'.
 
For my little test there I aerated the 5 litres overnight. (Early on in my history here someone told me to test pH after letting the water sit over night - for me there is negligible change. I need to aerate to get the 'natural pH' to show itself). The potassium carbonate was very soluble but all the same I let the bucket aerate and mix it up for 15 to 20 mins (it was pretty much dissolved inside 5 mins). I then cleaned out my test tubes and lids three times with the solution I was about to test before doing the testing. I don't think I made a mistake but I didn't double check because of my dilligency and because the pH was really so very high - I mean if I was slightly off the pH would have still been very high.
 
When speaking about my variable water LFS have suggested RO because it is stable and a common starting point. I don't want to go that route tbh. I do see my very soft water as RO like and that is where the dolomite lime experiments will go. Another LFS (who got a bit indignant when I didn't follow his advice) said 'just add crushed oystershell in a bag' but that wasn't good enough as the fresh water pH (and TDS) would have no relation to them - ie ever fluctuating pH, KH, GH. And at the end of the day this has all been primarily for one Betta who will likely be hard as nails! with the idea a few dwarf rasporas or such like to add a bit of sparkle.
 
This week I have got myself two large HDPE containers (180 litres between them) and solar waterpump and airpumps. My next plan is to fill them with tapwater, to have large reserves of similar/the same water so water changes will be pretty stable for a good while. I may even be able to refill or top them up with similar water. What water I will use is still in the air. I could use the hard water, the soft water and do my dolomite lime experiments (hence the pumps for large volume mixing over probably days if not longer) or wait till I get 'somewhere in between' tap water - but I haven't seen that yet. It seems to be very soft or very hard. Or I could fill one with hard, one with soft, and then blend them for each waterchange. I will of course keep an eye on any changes ocurring in the containers.
 
All this for my 20 litre tank and Betta that I still have not bought yet  (tho I am also thinking of a few rili shrimp now). I think most people would not even consider bothering with variable tapwater and just go with whatever comes out.
 
With what you have said with regard to varying water would you just use whatever water was coming out the tap at the time of the (50%) water change?

 

[TwoTankAmin]

If you want to use crushed coral in a bag one way to avoid problems with water changes is to alter the wc regimen. Instead of one big change a week, do several smaller ones. That way there is less impact from new water. Another alternative is to pre-treat new water. Get a cheap hang on filter and a container such a a rubbermaid of appropriate size. Put a bag full of crushed coral in the filter and run it on the new water for a day or two before doing the water change.
 
If you are keeping the TDS pretty steady, then changes in pH should not matter. What can create problems with pH changes is when they end up at the extreme ends of acceptable ranges. I can keep my altum angels happy between 6 and 7 pH. They would be fine lower as well but much above neutral would be a problem. The reverse applies to hard water fish. You may be able to keep African rift lake fish happier between 7.5 and 8.5 pH and some would be fine in higher. What they would not like is a pH at neutral and especially not lower.
 
But in order to get swings of the magnitude such that if move water outside of the desired ph range, that triangle is having other, much more important, things change as well and they are what will usually be doing the damage a and the accompanying pH change is a "side effect" so to speak. I know of no way to alter the pH of water which does not required the accompanying change in other parameters. of course if one starts with ro/di water then you can do almost anything you want with things. But the question that remains would be is that "constructed" water good for the fish. Does it contain all that is needed for the fish and does it avoid things which would be detrimental to the fish?
 
In the end, most of us are ill equipped to know the specific mineralization of water which is "good" for any species. we can not break down the contents of that water unless we pay to have it done. In the end, we tend to rely on our tap and it is not until we experience problems which are hard to figure out that we start to delve into the miasma of water chemistry. And this si the reason for the oft repeated advice that one keep fish which work in one's tap rather than trying to change one's tap parameters so we can keep specific fish.
 
It took me over 10 year in the hobby with 10-15 tanks going before I was even willing to try change parameters so I could get wild altum angels. My tap is now basically pH 70.-7.1, TDS at 83 ppm (lower w/ big rains), Gh 5o, HK4o. When I brought the altums, they the went into pH 4.2, TDS in the low 30 s and as little GH and KH as possible. Despite using an ro//di unit etc., I still lost plenty of fish the first 2/3 tries. And I have a continuous digital monitor for temp., TDS and pH. (It took me over a year to get the angels from 4.2 to close to a neutral pH and to TDS in the 60s ppm as opposed to the 30s).

 

[BubblesLotsOfBubbles]

If you want to use crushed coral in a bag one way to avoid problems with water changes is to alter the wc regimen. Instead of one big change a week, do several smaller ones. That way there is less impact from new water. Another alternative is to pre-treat new water. Get a cheap hang on filter and a container such a a rubbermaid of appropriate size. Put a bag full of crushed coral in the filter and run it on the new water for a day or two before doing the water change.
 
If you are keeping the TDS pretty steady, then changes in pH should not matter. What can create problems with pH changes is when they end up at the extreme ends of acceptable ranges. I can keep my altum angels happy between 6 and 7 pH. They would be fine lower as well but much above neutral would be a problem. The reverse applies to hard water fish. You may be able to keep African rift lake fish happier between 7.5 and 8.5 pH and some would be fine in higher. What they would not like is a pH at neutral and especially not lower.
 
But in order to get swings of the magnitude such that if move water outside of the desired ph range, that triangle is having other, much more important, things change as well and they are what will usually be doing the damage a and the accompanying pH change is a "side effect" so to speak. I know of no way to alter the pH of water which does not required the accompanying change in other parameters. of course if one starts with ro/di water then you can do almost anything you want with things. But the question that remains would be is that "constructed" water good for the fish. Does it contain all that is needed for the fish and does it avoid things which would be detrimental to the fish?
 
In the end, most of us are ill equipped to know the specific mineralization of water which is "good" for any species. we can not break down the contents of that water unless we pay to have it done. In the end, we tend to rely on our tap and it is not until we experience problems which are hard to figure out that we start to delve into the miasma of water chemistry. And this si the reason for the oft repeated advice that one keep fish which work in one's tap rather than trying to change one's tap parameters so we can keep specific fish.
 
It took me over 10 year in the hobby with 10-15 tanks going before I was even willing to try change parameters so I could get wild altum angels. My tap is now basically pH 70.-7.1, TDS at 83 ppm (lower w/ big rains), Gh 5o, HK4o. When I brought the altums, they the went into pH 4.2, TDS in the low 30 s and as little GH and KH as possible. Despite using an ro//di unit etc., I still lost plenty of fish the first 2/3 tries. And I have a continuous digital monitor for temp., TDS and pH. (It took me over a year to get the angels from 4.2 to close to a neutral pH and to TDS in the 60s ppm as opposed to the 30s).

 
 
Well with the dolomite lime I see it as a way water is naturally hardened so I'd be surprised if something 'bad' happened. I'm only after a KH of around 5 at the end of the day. I don't know where it will put the pH but hoping it would not be that high. If it is, then reevaluate the situation.
 
Interesting timescale (a day or two)  for the oyster shells to approximate the tank water. I thought it would need a week or two, but that is promising for any steps I make with the dolomite lime - I won't have to wait weeks to see what quantity has what effect.
 
"the oft repeated advice that one keep fish which work in one's tap"  I have read that manytimes so it appears my tap water is very atypical of the vast majority.
 
Anyway my pumps arrived today and they are working fine. I can gas off large quantities in the background. I feel happier dealing with these large water butts than messing around with 10 litres of 'something different' out the tap every week.
 
Oh I was targeting large singe water changes rather than several smaller btw to better control my nitrates (which seem to increase out of proportion with my ammonia input).