# KH Questions ????



## nswhite (Aug 25, 2006)

I have a 75gal fully planted tank with 2wpg. I dose th EI method. But my problem is with my KH I changed the substrate to a very nice SoilMaster Select (charcoal) and since then my KH has been way to low. It started out at KH:2 with an aquarium pharm test kit. So I added a little baking soda 1tsp. that brought it up to KH:3 and my pH:6.5. So then I thought everything was ok I test my water the next day and get a KH:2 again so I again add a little baking soda to bring it back up to KH:3. Why is this happening? Am I going to have to add baking soda to my tank everyday? I have a single fish in the tank just so you know. 

Current water peremeters as of this morning are below. Yesterday I added a tsp of baking soda to get the KH to 3 but the figures below show you what it is at now. I dont understand how come the KH keeps dropping. and by the end of the day the pH will drop to 6.2 or so becuase of my co2 injection, is this right? I'm confused so any input to steer me in the right direction would be great this is my first planted tank and I'm still going through the learning process.

pH:6.8
KH:2
GH: 7


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## Mud Pie Mama (Jul 30, 2006)

Here's my reply to another person having this same issue back in November:

"When I initially started two tanks with Soilmaster I found that my KH declined. I think this may have been due to the extremely porous nature of the Soilmaster granules. At first I replaced it with some baking soda, then I added half a bag of Onyx sand into each tank since its known to temporarily raise carbonate hardness. (I also found it on clearance at the store!) This seemed to help.

I think the effect is temporary."
__________________
Here' that thread:
http://www.aquaticplantcentral.com/...es/33274-soilmaster-select-ph.html#post246518

Thadius65 did not keep this thread updated, however he posted the same question over at T.P.T.Forum and there he later posted that he was "rounding the corner".

You can use the search function and "Soilmaster" to look for more reports about folks experience with it.


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## Satirica (Feb 13, 2005)

Is there a particular reason you are trying to raise the KH? I have a KH that hovers around 1.5 and plants/fish are fine with CO2 injection.


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## nswhite (Aug 25, 2006)

Mud Pie Mama said:


> Here's my reply to another person having this same issue back in November:
> 
> "When I initially started two tanks with Soilmaster I found that my KH declined. I think this may have been due to the extremely porous nature of the Soilmaster granules. At first I replaced it with some baking soda, then I added half a bag of Onyx sand into each tank since its known to temporarily raise carbonate hardness. (I also found it on clearance at the store!) This seemed to help.
> 
> ...


Ya I read this whole thread but it isnt any help and I'm not looking for a temporary fix I want a permanant fix thats why I asked the questions I also searched SoilMaster and only got 2 or 3 threads that where no help at all.

Also I have a 5" Elongatus that needs a KH at least KH:3

So is there anybody who can help? Can someone answer my question on why the KH keeps droping. It drops after about 12 hrs after if I put in baking soda? Need help please is it ok to add baking soda everyday?


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## Glouglou (Feb 21, 2006)

*KH Story...*

I will try with you to understand wat's happening here...

I think, will should go with a KH (alkalinity) general definition to have some idea of the process...

What is alkalinity?

Alkalinity in the chemistry of natural waters is a measure of how much acid (H+) is required to lower the pH to a specific level. This will be"total alkalinity." frequently referred to as TA.

TA is defined as the amount of acid required to lower the pH of the sample to the point where all of the bicarbonate [HCO3-] and carbonate [CO3--] could be converted to carbonic acid [H2CO3]. This is called the carbonic acid equivalence point or the carbonic acid endpoint.

These equations show what happens to carbonate and bicarbonate as acid is added:

(1) Buffer zone ==> H+ (acid) + CO3 (carbonate) ** ==> * HCO3- (bicarbonate)
- here as you add acid it is buffer by carbonate... ph will be stable

as you add more acid...

(2) carbonic acid endpoint ==> H+ (acid) + HCO3- (bicarbonate)* ==>* H2CO3 carbonic acid
- Here, all the carbonate is transform in bicarbonate and finally in carbonic acid by continued acidification, ph will drop.

Now! let see what you do...



> It started out at KH:2 with an aquarium pharm test kit. So I added a little baking soda 1tsp. that brought it up to KH:3 and my pH:6.5. So then I thought everything was ok I test my water the next day and get a KH:2 again so I again add a little baking soda to bring it back up to KH:3. Why is this happening?


You're numbers show that you have already a low concentration of carbonate buffer, at Kh:2,with ph 6.2

You add a little bit of carbonate buffer as Sodium Bicarbonate -> NaHCO3, result your KH go up at Kh:3 an sodium add to you GH reading as well. The PH go up for a while until acidity from add CO2, bacterial respiration, peat or others acid source transform all the bicarbonate you add in carbonic acid.
There it come back to youre old reading KH:2 / ph: 6.2, this is a kind of temporary equilibrium of your particular setup.

Here the buffer capacity is in a temporary equilibrium with all the acids sources present in your tank.

If you keep adding the buffer and decrease the acids input, you're Kh and ph will go up and established himself, after a while to a new (equilibrium).


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## hoppycalif (Apr 7, 2005)

My opinion is that a tsp of baking soda in 75 gallons of water isn't enough to raise the KH by very much. I think you get a very short duration rise in KH until equilibrium conditions exist again, after a few hours, then the KH is only slightly higher. I found that situation when I had my 29 gallon tank and was obsessing over having a higher KH. Now I just ignore KH unless I want to know it for some reason. I doubt that there are more than a very few plants or fish that care if the KH is 2 or 4, just as long as changes are not abrupt.


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## Jane in Upton (Aug 10, 2005)

Hmmm, I've also had the disappearance of kH in a tank I recently set up using Soilmaster Select. I've been getting an alkalinity reading from the Mardel test stips of below 80 ppm. Dennis has been kind enough to do a more robust test of my water (thanks Dennis!) using a Lamotte test kit, and he's come out with an alkalinity of 0 (ZERO!). 

He suspects its related to the Soilmaster Select's interaction with +ions (it has an extremely high CEC). 

Can anyone go into a bit more explaination of this? Its been a long time since college Chem!

Thanks!
-Jane


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