# does sandstones alter PH?



## SCMurphy (Oct 21, 2003)

It depends, generally it is best to avoid sedimentary rock as they have a tendency to turn to 'jelly' when submerged. Sandstone might not be just 'sand' it could have some limestone mixed in.


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## 2wheelsx2 (Jan 27, 2006)

In general, sandstones will have calcareous "cement" which bonds the grains together. If the cement is low, the sandstone will be crumbly and start falling apart in the tank, leaving lots of loose sand. You'd be better off getting shales or mudstones for the tank if you like the stratified look without the concerns.


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## ColinAnderson (Jun 25, 2004)

As far as I know, slate is also a good aquarium rock, and won't alter your water chemistry in any noticeable way.


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## 2wheelsx2 (Jan 27, 2006)

ColinAnderson said:


> As far as I know, slate is also a good aquarium rock, and won't alter your water chemistry in any noticeable way.


Correct. Slate is metamorphosed siltstone/mudstone and should have very little in the way of carbonates.


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## ColinAnderson (Jun 25, 2004)

Cool. I actually went out a while back looking for some slate, but ended up buying this artificial rock that looks a lot like slate, but was ridiculously cheap. I bought it from a business that specialized in building ponds, like you'd use in your garden. It doesn't alter the water chemistry in any way either.


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## daFrimpster (Mar 7, 2005)

I have had sandstone in one of my tanks for about 10yrs. It hasn't caused any problems. YMMV


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## bgoodwins (May 3, 2007)

SCMurphy said:


> It depends, generally it is best to avoid sedimentary rock as they have a tendency to turn to 'jelly' when submerged. Sandstone might not be just 'sand' it could have some limestone mixed in.


While your assertion has some truth to it, i wouldn't say that its really a fair generalization. I'm a geologist, rocks are my thing, so I'd say that unless your tank is filled with hydrochloric acid that you're gonna be fine adding your sandstone, even if it has calcareous intergranular cement. This is only for natural sandstones though, if its manmade, all bets are off. And even if it has pure limestone (calcium carbonate), the amount that would dissolve out of the pores would barely be enough to register on any kind of hardness test kits you have. I'm still of the opinion that the limestone dislike is more stylistic than a chemical detriment.


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## 2wheelsx2 (Jan 27, 2006)

bgoodwins said:


> While your assertion has some truth to it, i wouldn't say that its really a fair generalization. I'm a geologist, rocks are my thing, so I'd say that unless your tank is filled with hydrochloric acid that you're gonna be fine adding your sandstone, even if it has calcareous intergranular cement. This is only for natural sandstones though, if its manmade, all bets are off. And even if it has pure limestone (calcium carbonate), the amount that would dissolve out of the pores would barely be enough to register on any kind of hardness test kits you have. I'm still of the opinion that the limestone dislike is more stylistic than a chemical detriment.


Hey, another geo. I beg to differ with you though. I am out here on the west coast of Canada (Vancouver), and if you put a piece of limestone in our water, you'd be able to read something after a day. Since we live in a natural rainforest, our water is essentially rain water, and had very little dissolved minerals (GH and KH around 2). I put a piece of tufa (coralline) rock in my 20 gallon tank (fist sized) and within a week, my GH and KH went up 4 degrees. I use it to buffer the water since I am injecting CO2.

So unless your local water is hard, limestone will definitely affect the water.


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