sea shells

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sea shells

Post by colene harri » Thu, 23 May 2002 02:51:32



Hello and thanks to everyone that has answered my posts in the past.  This
group is great!! What can you all tell me about using sea shells in ponds
and aquariums?  Do I recall correctly that they will raise PH ?  Thank you
all once again...Colene
 
 
 

sea shells

Post by Rod Farl » Thu, 23 May 2002 19:20:16


Quote:

>What can you all tell me about using sea shells in ponds
>and aquariums?  Do I recall correctly that they will raise PH ?

Shells are aragonite (calcium carbonate).  To the limited extent they
may dissolve, they'll increase hardness (GH), alkalinity (KH), and pH.

The rate at which they dissolve is highly dependent on pH.  It slows
by a factor of 100 for each unit pH is raised.  So they do dissolve
rapidly in acidic water (pH below 7), but as pH approaches 8, the
rate of dissolution becomes negligible.  It will not raise pH above 8.3.
So the dissolution is self-limiting, and one cannot "overdose" a pond
with calcium carbonate.  It simply stops dissolving automatically.

If your pond has low pH or soft water, they will dissolve and improve
water quality.  If your pond pH is 8 or above to start with, or if your
pond water is hard, they might not dissolve at all, and won't affect
anything.  

So in the best case, they're beneficial, and in the worst case, they're
harmless.
- Rod

 
 
 

sea shells

Post by dr-s.. » Thu, 23 May 2002 22:42:14


are they pure Ca carbonate or a mix of calcium and magnesium?  INgrid
Quote:


>>What can you all tell me about using sea shells in ponds
>>and aquariums?  Do I recall correctly that they will raise PH ?

>Shells are aragonite (calcium carbonate).  To the limited extent they
>may dissolve, they'll increase hardness (GH), alkalinity (KH), and pH.

>The rate at which they dissolve is highly dependent on pH.  It slows
>by a factor of 100 for each unit pH is raised.  So they do dissolve
>rapidly in acidic water (pH below 7), but as pH approaches 8, the
>rate of dissolution becomes negligible.  It will not raise pH above 8.3.
>So the dissolution is self-limiting, and one cannot "overdose" a pond
>with calcium carbonate.  It simply stops dissolving automatically.

>If your pond has low pH or soft water, they will dissolve and improve
>water quality.  If your pond pH is 8 or above to start with, or if your
>pond water is hard, they might not dissolve at all, and won't affect
>anything.  

>So in the best case, they're beneficial, and in the worst case, they're
>harmless.
>- Rod

 
 
 

sea shells

Post by Rod Farl » Fri, 24 May 2002 23:27:52


Quote:

>are they pure Ca carbonate or a mix of calcium and magnesium?  INgrid

Shells are pure aragonite, calcium carbonate.
The can metamorphose into dolomitic limestone, if the groundwater
supplies magnesium from weathering of overlying igneous rock.  But
they wouldn't be shells anymore, they'd be rock.
- Rod