# Pros and cons



## Aurora (6 Mar 2016)

What would be the pros and cons of using found rocks? 
II've by the sea and there are some very pretty rocks. Could I boil them to get rid of the salt for my fresh water tropical fish?


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## Tim Harrison (6 Mar 2016)

I suppose it depends on what they're made of and how hard and inert they are. 
My current low-energy is scaped with cobbles collected from the beach. So far no problems.


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## Aurora (6 Mar 2016)

I have tried to upload a picture. But it says it's too big. I'll try again.

Did you boil them first to rid them of salt?


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## Tim Harrison (6 Mar 2016)

No, I left them outside for a couple of years before I used them...
That's not a recommendation tho', just never got round to using them until recently


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## Aurora (6 Mar 2016)

Ah ha that looks lovely.


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## Tim Harrison (6 Mar 2016)

Thanks, see if you can upload a pic of your rocks maybe someone can give you a more definitive answer.


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## zozo (6 Mar 2016)

Boiling them if possible is always a good idea, kills off any unwanted microbes and or fungus etc. especialy if it is porous or rock with cracks.. If it is a relative smooth surface non porous rock a good clean with a hard brush in hot water will do as good.. After they are clean throw some vinigar on it, if you see the vinigar start to foam and bubble it might be not a good idea to use them. 

If it does react to vinigar, but still like them to much, you need to test them to keep them submersed for a few weeks and do a before and after kH and gH test to see if this changes significantly. Some type of rock do others don't. Little changes are ok, if you do regular weekly water changes anyway it doesn't have much negative effect.
But rule of thumb is, if it reacts to vinigar let it be and search on.

But there is nothing more satisfying to enjoy watching a nice creation with things you found in nature yourself.


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## Aurora (6 Mar 2016)

Super advice.
Still can't seem to upload a picture.  Keeps saying it's smooth large. It's just a snap I took on my phone!


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## Paulo Soares (7 Mar 2016)

Evening,
You just can´t use a "salt rock" in a sweet water tank. Forget it.. 
No matter how much you boil them there always salinity in it. It´s in is composition - kind of genetics. Copy?

A geology consulting on kinds of rocks and it´s formation and you´ll find de answers. 

Best regards


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## dw1305 (7 Mar 2016)

Hi all,





Paulo Soares said:


> You just can´t use a "salt rock" in a sweet water tank. Forget it..
> No matter how much you boil them there always salinity in it. It´s in is composition -


Not necessarily, if they are rounded cobbles? They will be a hard impermeable rock, and when you rinse them you will have washed away all the salt (NaCl).

Salt (NaCl) is really soluble, which is why it has ended up in the sea.

cheers Darrel


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## zozo (7 Mar 2016)

Lately i found a batch of Stromatolites for sale, very beautifull rock and immediately thought of putting it in a tank of course. Couldn't hold it in my hand as was an internet sale, but after some researching i did skip it for now.. It's formed from fossilized bacterial deposits such as cyano bacteria, sand grains and contains probably shellfish residues.. thought it was kinda cool  having that in a tank.. This is commonly found on beaches and sea shores.. But still have no real idea if it would be useable. Maybe since it is fossilized, but i guess shellfish particles still contain loads of calcium and magnesium.


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## PARAGUAY (7 Mar 2016)

dw1305 said:


> Hi all,Not necessarily, if they are rounded cobbles? They will be a hard impermeable rock, and when you rinse them you will have washed away all the salt (NaCl).
> 
> Salt (NaCl) is really soluble, which is why it has ended up in the sea.
> 
> cheers Darrel


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## PARAGUAY (7 Mar 2016)

Thats great to know Darrell as I have a lot of well worn beach cobbles, think you said previously probably carbonate limestone, anyway they pass the vinegar test and seem inert


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## Paulo Soares (8 Mar 2016)

Darrel, 
Not necessarily ok. But you can´t determine the concentration of mineral salts of each rock.. you can boil a rock a couple of times, do some testing, conclude that all it´s ok and put the rock in a layout. 
A couple of weeks before or more, surprisingly you notice salt water in the tank ... 

And then you wonder why.. or how?
This hapens to me. 

You ´ll never know. Is it worth to take the risk? 
Those rocks are being "Salty" for millions of years..  
You don´t dissolve the salt in it so easily not even erradicate it.. i would say you jus´t can´t. 
No matter how much you boil there´s always will be some salt remainin that will be realeased in time and more.. some how grow in the stone it self. This part i can´t explain. I´m not geologist. But they explain this. 

It´s my opinion Darrel. 

Cheers.


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## dw1305 (8 Mar 2016)

Hi all,





Paulo Soares said:


> But you can´t determine the concentration of mineral salts of each rock..


 Honestly you don't need to, if it is a smooth, round cobble, it won't contain any sea salt (NaCl) in the rock matrix, only very hard rock will become rounded, and very hard rocks are impermeable. 

If you have a conductivity meter you can just look for changes in conductivity. When you put the rocks into soak in fresh water initially you will get a rapid rise (as any NaCl goes into solution), but after that water has been changed conductivity shouldn't rise at all. If conductivity creeps up slowly then you probably have a carbonate rock.

Carbonate rocks won't dissolve in the sea, because the sea is both carbonate rich and alkaline, but limestone can only become rounded cobbles if they are extremely old and hard (like Carboniferous age limestones), you won't find rounded Oolite or chalk cobbles, they aren't hard enough rocks. Carboniferous age limestone won't have much effect on pH, or conductivity, because they have been compressed and are now very hard. They are over 300,000,000 years old, if they were soluble to any large extent they would have long ago have dissolved away.





Paulo Soares said:


> you can boil a rock a couple of times, do some testing, conclude that all it´s ok and put the rock in a layout. A couple of weeks before or more, surprisingly you notice salt water in the tank ..


 This can happen if you have a rock with pore spaces, or voids, in it.

If it is a smooth sea cobble it won't have these, because porous rocks wouldn't have formed a cobble in the first place.

cheers Darrel


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## zozo (8 Mar 2016)

It's of course always a good advice to have some degree of healthy paranoia when you do not know what you are holding in your hands. I would always test for some time anyway if this is the case. 

I'm using a known limestone in my  tanks, still a relative hard rock containg white vains, looking like quartz but it is chalk deposites, in geologic terms still relative soft..This is a sedimentary rock formed by ocean deposites, like most limestones are and it's not uncommon to find marine life fossils in those quarrys. Sedimentary rocks are commmonly the softes because they are formed in layers as igneous rocks is formd by  a melting process and commonly the hardstone category like granite. 

My limestone reacts heavily to any kind of acid i put it in, i kept it in deluted muriatic acid  for a week and parts of it where just eaten away. It's a kind of rock any aquarist would throw as far away as he can after seeing this..  But still I tested it for months in the water and it doesn't leach anything fast enough to make it measurable with a weekly 25% water changes. I even tested it for a month without water changes and i didn't measure any changes in ph, kh nor gh. Also plantgrowth was not noticable affected.

So imho, Cons are if you are not sure you need to test before taking risks, this takes some time.. Pros are if you do this you'll learn, e.g. that sometimes things previously thought impossible or not good aren't always as drastic as portrait. 

Intresting topic actualy.. I wonder and ask myself now, why rock formed by oceanic deposites doesn't contain salt? We even have clay balls sold as pond and aquarium fert balls which are quarried from oceanic blue clay depostis. I never noticed it leaching salt, probably doesn't do with negative effect else it would be sold as fert ball for aqautic plants.



Paulo Soares said:


> This hapens to me.


Have you ever try to find out what type of rock it was??


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## ian_m (8 Mar 2016)

zozo said:


> I wonder and ask myself now, why rock formed by oceanic deposites doesn't contain salt?


Because the carbonate has undergone pressure and heat whilst under the earth and the salt has been reacted with other constituents. Digging around on Google reveals 0% NaCl in limestone.

Anyway if it did survive, most would be embedded in the rock, thus not available to be dissolved in water.


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## Aurora (8 Mar 2016)

Wow thanks! Some great info 

Still can't upload a pic tho lol


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## zozo (8 Mar 2016)

ian_m said:


> Because the carbonate has undergone pressure and heat whilst under the earth and the salt has been reacted with other constituents. Digging around on Google reveals 0% NaCl in limestone.
> 
> Anyway if it did survive, most would be embedded in the rock, thus not available to be dissolved in water.



That's what i thought as well, i didn't think of searching NaCl in limestone.. Thanks.. 

If it did, embeded ok, as long as you don't break it in to pieces, than it would surface. But 0% says enough.. 

But there seem to be salts in limestones, enough to write a booklet about it..
Water soluble salts in Limestones and Dolomites.

As i experience with the my limestone, using a solid piece of rock for testing the leach/time ratio wont be mesearable enough. So they grinded it in boiled distilled water.
Unfortunately it's tested in the USA and is my Ardenne Limestone not listed.


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