In saltwater a small electric current can be passed through a metal framework causing limestone, calcium, salt and other minerals to accrete and form bio-rock
Freshwater does not conduct electricity as well as saltwater and I am assuming that this is why I can find no reference to freshwater bio-rock.

Could we not take a conductive framework, make it covered in conductive hairs, and then coat it with a slow-release salt coating to change the salinity of the water only around the electrified framework?

Freshwater has limestone, and calcium and other minerals just no salt.

As the salt dissolves around the conductive protrusions of the electrified framework, current flows through the inner core but also plays along the outer hairs in tiny St. Elmo's fire discharges.
The salt dissolves around individual hairs first as each one corrodes creating a tubular lattice of solidified minerals including the salt itself if time released at the right rate.

<shrugs>

Would it work?
-- 2 fries shy of a happy meal, Mar 15 2024

Minerals in Water https://study.com/c...003849637991278.png
Surprisingly scarce info on fresh/sea water comparisons [neutrinos_shadow, Mar 15 2024]

See linky.
Fresh water (by it's very nature) doesn't have much of anything in it.
Maybe you just need a higher voltage? (Channeling [8th of 7] here...)
Although you might be working a vicious circle here: putting on a salt coating so it will dissolve & create a salt coating..?
-- neutrinos_shadow, Mar 15 2024


Maybe you could make your bio-rock in an estuary. If you can make it form full of air pockets, like pumice, then you can make it float, and tow it upstream to the trout pond.

You might be able to charge tourists for the experience of being a gondolier on a raft made of rocks.
-- pertinax, Mar 15 2024


Cool link.

So... I'm thinking, longer time = same concentration of minerals, or greater voltage/amperage, salinity, magnetic field tests reveal... something.

So where are the experiments to be found?

I can't find them.
-- 2 fries shy of a happy meal, Mar 15 2024


Just thinking ...

Evian rocks
Perrier rocks
San Pellegrino rocks
etc.
-- pertinax, Mar 15 2024


I made some initial stabs at being a vegan and some people live off the natural, much higher calcium in mineral water. Still, the levels of calcium on offer in sea water makes me wonder just how much sea water is still safe to drink.

I think a bull shark pond would make the salt water/sea water dichotomy moot, while making the limestone boat rides much more exciting.
-- 4and20, Mar 15 2024


//Freshwater has limestone, and calcium and other minerals just no salt//

Limestone is calcium carbonate, which is a salt. There are many salts. Freshwater can be considered as water distilled off the ocean/other wet places and sprinkled over the land by rain where it runs downhill back to the ocean. Along the way it picks up various substances to different extents, depending on local conditions. But, not very much. Aside from the sodium and chloride, (those are super soluble, hence why the sea has so much of it,) the ocean is more or less a saturated solution of calcium and magnesium. For this reason, you only need a slight tweak to conditions and calcium/magnesium can be convinced to precipitate out of solution. This is exploited by various sea creatures, tweak the conditions slightly and you have solid calcium carbonate, do it in the right place and you have a shell or some bones.

Freshwater has 10-50 fold less calcium & magnesium (as Ca2+ & Mg2+ respectively). Obviously there are freshwater creatures with shells and bones, but they have to work a lot harder to achieve shells etc, and that's why there aren't any hard freshwater corals.
-- bs0u0155, Mar 15 2024


As an addendum, I do like the term "Bio-Rock". I think I might steal it.

Overall, life on Earth has been doing a scarily efficient job of taking the atmosphere and turning it into rock. Originally, Earth had a CO2/CH4/N2 atmosphere. There's trapped bubbles and a few reasonable proxies that give us ideas about the proportions of gasses in the atmosphere but not much (almost 0) evidence on how MUCH atmosphere there was in terms of pressure/density. But what we do know is that all the methane is gone, and all but the tiniest fraction of CO2 is gone. So all that carbon and H2 is where? Rock, billions of tons of limestone, sand (calcium carbonate & silicon dioxide) Coal, oil etc. On top of that, removing CO2 led to O2, which spent millions of years reacting with everything it could forming oxides of all the metals (Iron/Aluminium etc.) pulling more gas out of the atmosphere and making more rock.

A relatively recent evolutionary adaptation is plants that can grab nitrogen directly out of the air. Nitrogen and the scarily reactive O2 is all there's left! When will these dangerous light-powered atmosphere wrecking organisms be stopped?
-- bs0u0155, Mar 15 2024


//I think a bull shark pond would make [...] boat rides much more exciting.//

Not necessarily; the bull shark population of the Swan River recently went about 50 years without killing anyone. (Mind you, they did kill someone quite recently, just to remind us all that they're still there).
-- pertinax, Mar 16 2024


Totally cool info [bs0].
-- 2 fries shy of a happy meal, Mar 17 2024


//Biorock was protected by a trademark between 2000 and 2010//

I'm thinking of it as a catch-all term for rocks of biological origin, either directly or via biological action. E.g. limestone from algae/shells directly or because it precipitates out due to ocean alkalinization from atmospheric CO2 disappearing. Sandstone is a similar story.

Maybe there's already a term for this, I need a chat with a geologist. That would have been easy when I worked at a proper university, take a stroll to one of the uglier pubs with the cheaper beer in the 1960's concrete half of the university and look for someone with practical boots, a beard and who's clearly been outside for half the week.
-- bs0u0155, Mar 18 2024



random, halfbakery