# Soft water, CO2 and glosso Qs



## gf225 (Mar 26, 2005)

Are most plants fussy regarding hardness of water?

And as a side issue, is more CO2 required in hard water, to reach a specified level when compared to soft water?

I'm setting up a 120cm pure glosso iwagumi 'scape for a friend. We have the option of using RO. His tap is hard - GH 15+. Would RO be better?

Any thoughts welcome.


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## Aen (Jul 24, 2007)

Glosso grows better in soft water.


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## Edward (May 25, 2004)

It's not the GH that bothers some plants, it is high KH. Using RO is very nice because of the complete water parameter control you have. You can add CaSO4 dry to 30 ppm and easily maintain it. Then PPS-Pro can add proper Mg supplementation without the risk of increasing Mg related GH. It also depends on your substrate if it is inert.


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## gf225 (Mar 26, 2005)

Thanks.

Why does high KH bother some plants? (Why does glosso grow better in soft water?)

And what about CO2? Is more needed for higher KH, as per my OP?

CaSO4 to 30ppm? 30ppm what?


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## hoppycalif (Apr 7, 2005)

It takes the same amount of CO2 to reach 10 ppm in water whether the water is soft or hard, whether KH is low or high.


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## gf225 (Mar 26, 2005)

hoppycalif said:


> It takes the same amount of CO2 to reach 10 ppm in water whether the water is soft or hard, whether KH is low or high.


Thanks Hoppy.

That's what I've experienced, personally. I've run RO to 2dKH, and tap to 15dKH, 1BPS CO2 gives me 30ppm with both.

But what I have read, from numerous sources, some "official", is different.

Any ideas why high KH adversely affects some plant growth?


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## Aen (Jul 24, 2007)

Simple, Glossostigma elatinoides originates from soft/medium water and have evolved biologically to suit these conditions.


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## gf225 (Mar 26, 2005)

Aen said:


> Simple, Glossostigma elatinoides originates from soft/medium water and have evolved biologically to suit these conditions.


What processes for growth are inhibited and why with a high KH?

Not so simple...


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## JamesC (Jul 26, 2005)

gf225 said:


> That's what I've experienced, personally. I've run RO to 2dKH, and tap to 15dKH, 1BPS CO2 gives me 30ppm with both.
> 
> But what I have read, from numerous sources, some "official", is different.


George, what you have read from other sources is correct. The higher the KH the more CO2 is required to lower the pH by the same amount. In practice though you probably won't notice any difference in the ranges we deal with.

James


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## hoppycalif (Apr 7, 2005)

Lowering the pH by a specific amount isn't the same as adding a specific concentration of CO2 to the water. Our goal is a fixed ppm of CO2, not a lowering of the pH by some specific amount.


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## JamesC (Jul 26, 2005)

Yep, you're right I didn't phrase it correctly. I should've said it requires more CO2 to be added to water with a high KH than with a low KH to obtain the same CO2 levels. The differences are quite small with the KH levels we deal with so I'm really only nit picking 

James


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## Aen (Jul 24, 2007)

gf225 said:


> What processes for growth are inhibited and why with a high KH?
> 
> Not so simple...


You cannot change Glossostigma's preference for soft water, just like you cannot make a herbivore eat meat, have land plants grow in water, make Malawi cichlids live in the Amazon...


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## uglybuckling (Jun 28, 2004)

Aen said:


> You cannot change Glossostigma's preference for soft water, just like you cannot make a herbivore eat meat, have land plants grow in water, make Malawi cichlids live in the Amazon...


*fires up the trusty gene splicer* Wanna bet?

In all seriousness though, when gf225 asked, "What processes for growth are inhibited and why with a high KH?" I think the answer s/he was looking for is the chemical reasoning underlying how high KH hurts plants.

A high KH means there's a lot of calcium in your water.

Now, if I'm remembering my biochem and botany classes correctly (and correct me if I'm wrong here, they were a long time ago), the transporter by which plants pick up Calcium is not very specific for this ion.

Irrelevant tangent: This is the mechanism underlying magnesium and potassium toxicity in plants--if plants OD on K or Mg, they don't get enough calcium--and this in turn is the reason why there's some desert with magnesium-rich soil somewhere or other (I can't remember currently) that can't be converted to arable farmland no matter how much water they move into it.

Anyway, getting back to the point, conversely, if you have TOO MUCH calcium, in the form of a high KH, the plant gets confused and picks up the calcium to the exclusion of these other positively-charged ions, and hence can wind up with potassium or magnesium deficiencies.

--Bucky


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## hoppycalif (Apr 7, 2005)

KH means carbonate ions, not calcium. So, you don't necessarily have high calcium with high KH. You could have high potassium, sodium, magnesium instead. But, I suspect that natural bodies of water with high KH do have high calcium also.


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## gf225 (Mar 26, 2005)

Thanks Bucky and Hoppy.

Aen - I think you've misinterpreted my questioning. I agree with what you say though.


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