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Sand increases pH of water temporarily. What about long term?

KRMans

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21 Dec 2021
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I've seen comments that certain sands increase the pH level of the water initially.

Here is one example, and it's not the only one, which says: "Initially will slightly raise the pH of your water."

River Sand

I'd like to hear people's experience of using sand and rocks that initially increase or affect the pH of water. Does it correct itself later? Or is a permanent condition? Should this deter me from using this type of sand?

I'm actually thinking of using this river sand from Bunnings (in Australia), and am concerned that the above examples could indicate possibility that the river sand can increase the pH level of the water.

Bastion 20kg River Sand
 

hypnogogia

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The problem with that river sand is that you don’t k ow what it’s made up,of, so it may well continue to buffer over the long term. I’ve used river sand an and aquatic supply store and had great success with it and it didn’t raise Ph at all.
 

KRMans

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21 Dec 2021
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The problem with that river sand is that you don’t k ow what it’s made up,of, so it may well continue to buffer over the long term. I’ve used river sand an and aquatic supply store and had great success with it and it didn’t raise Ph at all.
So would it be safer to go with pool filter sand which I'm guessing, they select a sand that does not change the pH? (That's my guess. I don't know if they do. Does anyone know).
 

jaypeecee

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Hi @KRMans

I know precious little about sand but your question interested me. So I did a quick search and found the following:


You can download the file as a PDF or read it online.

If you take a look at Table 2 on page 26, it is a list of pH Test Data. River sand varies from 7.25 to 7.68.

I hope it goes some way to answer your question(s). I had always thought of sand as inert so this has also been a useful exercise for me.

JPC
 

Nick potts

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Torbay
As above, depends on what our sands are made of, coral sand for instance will buffer until it has completely dissolved, whereas river sand may only buffer for an unknown time.

Pool/silica sand is inert and won't affect your parameters.
 

Maf 2500

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5 Jan 2021
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Slade Dingle
Yes, any sand that is silica (or quartz) will not affect water parameters. It is the material left after long term weathering and therefore the most inert. Rio Negro for example has substrate of silica sand and does not raise the pH there!

Random river sand on the other hand could contain any minerals including carbonates due to local geography/geology.

Many brands of aquarium sand state they are made of quartz or silica and that they are neutral and will not add hardness. These are the ones to look for in the aquarium store. A product that states "Initially will slightly raise the pH of your water" is a red flag for me and roughly translates as "this sand is not very pure."
 

dw1305

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Hi all,
I had always thought of sand as inert so this has also been a useful exercise for me.
It isn't the silica content, sand is always mainly quartz (SiO2), but it could contain various amounts of mollusc shell (CaCO3). As an example sand from a beach in Western Britain will contain a large proportion of shell and <"maerl fragments">, along with the silica sand.

cheers Darrel
 

jaypeecee

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It isn't the silica content, sand is always mainly quartz (SiO2), but it could contain various amounts of mollusc shell (CaCO3). As an example sand from a beach in Western Britain will contain a large proportion of shell and <"maerl fragments">, along with the silica sand.
Hi Darrel (@dw1305)

Many thanks for the reply.

Yes, I was very much aware that sand is quartz/SiO2. But, I was overlooking the 'insoluble' impurities and it makes a lot of sense that CaCO3 would be high up on that list.

JPC
 
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