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Inert rock types
- Thread starter j.smet78
- Start date
Hi all,
If you have <"hard tap water"> (over ~17 dGH / 17 dKH), and <"don't add CO2">, then even limestone rocks won't dissolve, the water is already fully saturated with calcium (Ca++) and bicarbonate (2HCO3-) ions.
cheers Darrel
Granite, and similar quartz rich igneous rocks <"Igneous">, won't change your water chemistry - <"Aquarium sand and diatoms...">.
The easiest way to tell is just by shape. Basically any rock that is a <"rounded pebble or cobble"> won't, only old, really hard rock, forms water <"rounded spherical shapes">.
If you have <"hard tap water"> (over ~17 dGH / 17 dKH), and <"don't add CO2">, then even limestone rocks won't dissolve, the water is already fully saturated with calcium (Ca++) and bicarbonate (2HCO3-) ions.
cheers Darrel
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Connswater
Member
Thanks Darrel.
I hadn't clocked that rounded rocks are going to be non sedimentary but that of course makes perfect sense even to my mind with limited scientific knowledge, and I knew that very hard water meant that sedimentary and metamorphic rocks wouldn't dissolve but didn't know the cut off point was quite so high, but applies to me since, I have tap of water of roughly those Gh and KH and I of course live in an area where water comes off chalk.
Thank you, another learning day for me here, I'll be ready to sit an examination - O Level science for fish and plant keepers - well, some day, maybe in a decade. And using the phrase O Level shows my age yet again, though it is a very long time since I actually taught O Level...though the reverse grade structure of GCSE caused me a few headaches in my last few years in the classroom and at parents' evenings, another story and not for here.
If by the way, you ever organise a sewage farm tour to give an illustrated talk on aerobic bacteria, biological oxygen demand, safe effluent discharge into rivers, Tubifex worms etc., sign me up.
I hadn't clocked that rounded rocks are going to be non sedimentary but that of course makes perfect sense even to my mind with limited scientific knowledge, and I knew that very hard water meant that sedimentary and metamorphic rocks wouldn't dissolve but didn't know the cut off point was quite so high, but applies to me since, I have tap of water of roughly those Gh and KH and I of course live in an area where water comes off chalk.
Thank you, another learning day for me here, I'll be ready to sit an examination - O Level science for fish and plant keepers - well, some day, maybe in a decade. And using the phrase O Level shows my age yet again, though it is a very long time since I actually taught O Level...though the reverse grade structure of GCSE caused me a few headaches in my last few years in the classroom and at parents' evenings, another story and not for here.
If by the way, you ever organise a sewage farm tour to give an illustrated talk on aerobic bacteria, biological oxygen demand, safe effluent discharge into rivers, Tubifex worms etc., sign me up.
Hi all,
Granite is a really common rock, easy to identify and often for sale in Garden Centres etc.
Old sedimentary rocks (like Carboniferous Limestone <"Carboniferous Limestone - Wikipedia">) exposed at the surface are usually really hard, although there maybe more recent <"re-deposition of CaCO3 as tufa"> or travertine which would dissolve, but won't form cobbles etc.
Since the Cretaceous period a huge amount of chalk has dissolved, but there was an immense thickness to start off with. The <"North and South Downs"> are the surviving <"remants of a chalk dome">, where the dome top has eroded away in the last 70 million years.
cheers Darrel
They can be sedimentary, they just have to be really hard - <"Millstone Grit - Wikipedia">. Most igneous rock will be hard, it is only in <"exceptional circumstances"> that it won't be.
Granite is a really common rock, easy to identify and often for sale in Garden Centres etc.
Old sedimentary rocks (like Carboniferous Limestone <"Carboniferous Limestone - Wikipedia">) exposed at the surface are usually really hard, although there maybe more recent <"re-deposition of CaCO3 as tufa"> or travertine which would dissolve, but won't form cobbles etc.
So basically the water has dissolved all the limestone (CaCO3) it can already. All of us who have limestone aquifer water will have water of 17 - 18 dGH & dKH, that value is caused by the atmospheric CO2 level and is the equilibrium point at ~420 ppm CO2 - <"Trends in CO2 - NOAA Global Monitoring Laboratory">.
Since the Cretaceous period a huge amount of chalk has dissolved, but there was an immense thickness to start off with. The <"North and South Downs"> are the surviving <"remants of a chalk dome">, where the dome top has eroded away in the last 70 million years.
cheers Darrel
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Andy Pierce
Member
I use slate as an inert rock in one of my aquariums. Because of the fracture pattern of slate it doesn't really form rounded spherical shapes so much as blocky or flat shardy type of shapes and "chippings". You can get it in large flat sheets which is convenient for some purposes and it's relatively easy to cut using a diamond Dremel cutting wheel.
Is Rihno stone a bit of the same you think?
