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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?
richardcunliffe
Member
'Glimmer' petrified wood rock is also inert I believe (at least I've never had issues) and tends to be on the cheaper end. Admittedly, I think it's actually pretty challenging to scape well with
Hi all,
Cheers Darrel
Unlikely these days unfortunately, water companies aren't really <"encouraging visitors"> .......
Cheers Darrel
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Andy Pierce
Member
It's hard to know what 'rhino' stone is... this sort of terminology can easily be vendor-specific. It does not look like slate to me. "It is a sedimentary crumb rock with a beautiful blue shade and a minimalist structure on the surface." If that is to be believed it rules out slate. "a metamorphic rock from the Pleistocene period" Marketing droids just make all this stuff up. "Wild blue rhino stone is a premium bluish-gray cobblestone collected from the riverbed in Eastern Europe" maybe, maybe not. I definitely believe the "premium", as in premium price part.
Simon Cole
Member
... Oddly enough, that describes accurately rocks from the Larderello geothermal field in southern Tuscany (Italy). I had thought that Rhino Stone was some sort of carbonated mudstone, and I rather suspected that it was a marlstone. They do a lot of quarrying and drilling in that region and that has exposed quite a few riverbed seams of near-identical rock which indeed underwent metamorphism during the Pleistocene. Slate has a slightly different metamorphic progression from phyllite to schist then gneiss. Glimmer "petrified wood" rock is in the latter. Sadly it never was a tree. Welcome to the wonderful world of aquarium retail.
johntambler
New Member
Most common inert rocks for aquariums:
- Lava rock
- Dragon stone (Ohko stone)
- Seiryu stone (debatable, may raise hardness slightly)
- Basalt
- Granite
- Quartz
- Slate
Connswater
Member
As a kid, last year or two of primary school, my friends and I, those who had tropical aquariums, and there were at least five of us in our little group, used chiefly sandstone, inert, and not even metamorphic. We collected it from an abandoned quarry, sorry health and safety was largely ignored/unknown in my childhood. We also used metamorphic and granite, volcanic of course, we rather proudly knew that as kids, illegally collected from beaches, by bicycle, choppers and the like, dreadful bicycles, we realised that fairly quickly and slowly transitioned to more conventional bicycles. Funny how tropical fish provided an interest for so many of my contemporaries in the horrors of the early "Troubles" in Northern Ireland. Indeed one of my aquariums made on to TV as a symbol of 'life goes on', 1974 I think.
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I'm sure I have read somewhere that Frodo Stone is practically inert and after a while the effects become negligible. I am also quite sure that I have read/watched a tour of Adam Paszela's studio where he explained that the Frodo Stones were hand collected by aquarists from the Carpathian Mountains which I believe are largely sedimentary, so I don't know 🤷♀. I could also be wrong on all counts.
I’m normally the first to complain about dodgy marketing practice but honestly… it’s pretty much approaching impossible to find a set of such beautiful stones from wholesale retailers. The aquarium trade sure has a knack for getting really exceptional shaped pieces.
Hi all,
A road trip to Skye perhaps? <"Geological field trip through Scotland: Basalts from the Isle of Skye">.
cheers Darrel
You could "Pick You Own"? <"Probably not legally"> and definitely <"not anywhere near Kent">.
A road trip to Skye perhaps? <"Geological field trip through Scotland: Basalts from the Isle of Skye">.
cheers Darrel
Connswater
Member
A long way, from Kent, but well worth it I'm sure.
Hi all,
And maybe pick up some other landscape material while you are there? <"Sourcing woods..">?
cheers Darrel
I think if you are a geologist Skye has a lot to offer.
And maybe pick up some other landscape material while you are there? <"Sourcing woods..">?
cheers Darrel
