# Soilmaster ph/kh questions.



## treefish (Oct 10, 2007)

How long can I expect low ph/kh when using SMS? 

Indefinitely?
A few months?
Years?
Eons?


Where does the kh go exactly? Is there some kind of chemical reaction, or is it stored in the substrate? If it's the latter, I assume it has a max capacity, yes?

What is it that changes the ph?

So, are these just permanent characteristics of SMS, or will it one day neutralize and stabilize itself?


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## hoppycalif (Apr 7, 2005)

Soilmaster is not made to be used as a substrate, even though it works well as one. So, the qualities that are controlled in the manufacturing process must not include the qualities that lead to the change in pH/KH. The SMS I use has never had such an effect on the water, but I bought it about 3 years ago. I don't think there is any way to say what the SMS someone buys today will do to the pH/KH, let alone say how long the effect will last.


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## goalcreas (Nov 20, 2006)

I had schultz aquatic soil lower the ph/kh for about 4 weeks with water changes about every 4 days.

I would expect the Schultz (Very similar to SMS and made for under water planting) to be a little more controlled quality wise.
Maybe they started making / controlling the SMS the same way in past years?


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## orlando (Feb 14, 2007)

Ive had SMS for over 2 years in a few tanks and it stole my KH right out of the water. Like Hoppy siad, its not made for aquarium use. Who knows what go's on during the manufacturing process. 
After that, I stopped testing my water.
Now I dont worry.


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## treefish (Oct 10, 2007)

Hmm, I thought the ph/kh change was common to all SMS samples. The SMS I own is only being used for growing emersed plants right now. I haven't even bothered testing it. I just assumed the ph/kh would drop.

I am using Schultz aquatic soil in one of my tanks. I haven't ever really noticed any ph changes from it. If it has changed, it is negligible. I don't have a test kit for kh, so I have no idea if that has changed.

I will probably not worry about it either, but I was curious about any prolonged effects.

Orlando, since your batch did lower your ph/kh, and you've had it for several years, can you test it now to see if you get the same results?


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## orlando (Feb 14, 2007)

Yup still the same as of today. Although its not quite as fast at absorbing it. EI dosing helps with the water changes.


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## treefish (Oct 10, 2007)

OK thanks

I can kind of understand how the pH remains constant with this stuff, but still wonder where the KH goes.

I guess I'll test mine just to see, and forget about it after that.


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## JamesC (Jul 26, 2005)

SMS and other baked clay compounds are known as cation exchangers (CEC) or sometimes as hydrogen exchangers. This means they replace the Mg++, Ca++ and other cations in the water with hydrogen ions. It's these hydrogen ions, which are more commonly know as acid, which react with the KH and lower it.

Normally, depending on your water's GH, the KH and pH should settle down after a few weeks with plenty of water changes.

James


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## hoppycalif (Apr 7, 2005)

JamesC said:


> SMS and other baked clay compounds are known as cation exchangers (CEC) or sometimes as hydrogen exchangers. This means they replace the Mg++, Ca++ and other cations in the water with hydrogen ions. It's these hydrogen ions, which are more commonly know as acid, which react with the KH and lower it.
> 
> Normally, depending on your water's GH, the KH and pH should settle down after a few weeks with plenty of water changes.
> 
> James


I am a Chemistry Dummy, so:
If a high CEC material absorbs Ca++ from the water, where it is in equilibrium with CO3--, and gives up H+ ions in exchange, doesn't that leave the water still in equilibrium with H+ and CO3-- or HCO3-? (I think I am figuring out the answer as I write this, but...) So, is it the excess of H+ vs OH- that leaves the water acidic?

On the same subject: when a plant "eats" NO3-, what does it give up to the water in exchange for the NO3-? Or, does it take in both ions of the molecule containing the NO3-?

You have only yourself to blame for this! You let us know you know something about chemistry.


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## goalcreas (Nov 20, 2006)

Nice site you have there James, I bookmarked it for future reference.
Thanks


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## JamesC (Jul 26, 2005)

hoppycalif said:


> I am a Chemistry Dummy, so:
> If a high CEC material absorbs Ca++ from the water, where it is in equilibrium with CO3--, and gives up H+ ions in exchange, doesn't that leave the water still in equilibrium with H+ and CO3-- or HCO3-? (I think I am figuring out the answer as I write this, but...) So, is it the excess of H+ vs OH- that leaves the water acidic?


That is correct. pH is a measurement of the concentration of hydrogen ions in a solution, so the more you add the more acidic the solution becomes. CO3 and HCO3, or KH, are buffers and will to some degree try to reduce the effect of the added acid in keeping the pH stable.

There are different types of ion exchangers though. Not all replace cations with hydrogen ions. Water softeners for example are sodium exchangers so they replace Mg++ and Ca++ with Na+



hoppycalif said:


> On the same subject: when a plant "eats" NO3-, what does it give up to the water in exchange for the NO3-? Or, does it take in both ions of the molecule containing the NO3-?
> .


Biology was never my strong point but I believe that plants have to take in a equal amount of cations (eg Mg++) and anions (eg NO3-) to retain an internal balance. Others with more knowledge than me on this may wish to chip in.

Thanks
James


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## treefish (Oct 10, 2007)

Thanks for the great info James.

So, it is as expected, but not as I understood it (not that I had any idea to begin with). In theory, the pH/KH issue should eventually "settle down."



goalcreas said:


> Nice site you have there James, I bookmarked it for future reference.
> Thanks


Sure is! I'm bookmarking this one also.


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## JDowns (Jan 27, 2008)

I've never seen a KH drop with SMS. But with that said I've also never setup a tank without some type of buffering substrate added with SMS, most ofter either Onyx or Grey Coast Calcite (both of which are almost identical).

Here is a good analysis of different soils including SMS and/or Turface

One thing I never see addressed in detail either so its a bit confusing as to the level of the affects, would be the nitrificaton cycle, specifically nitrosomonas.

Biological Filtration Article


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