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re:Gravel... To wash or not to wash?

>I went to a local quarry the other day and picked up about 50 pounds of
>what they call "bird's eye gravel."  It's about 2-4mm in size and is nicely
>colored.  It is also extremely dirty, so I began to wash the gravel bit by
>bit so I could put it in my tank.  As I rinsed, I noticed that the water
>obtained a nice reddish brown hue as it washed down the drain.  At first, I
>was pleased at myself for doing such a good job of washing the gravel, but
>after awhile it began to occur to me that the nice reddish color was an
>indication that the silt mixed in with the gravel must have some level of
>iron in it.

You probably did ok to wash it.  If you hadn't purchased the gravel from a
quarry, I'd definitely say wash it, just to make sure that you get out most of
any chemicals that might have wound up in the gravel prior to, during, or after
packaging and shipment.

I'd go one step further and place about 2" of vinegar in a clear glass.  Then
add about 1/2" of your washed gravel to the glass.  If it fizzes, then it will
probably play with your water chemistry on you.  Fizzing indicates the presence
of carbonates, which will change your alkalinity and probably your calcium or
magnesium hardness as well.

A final test (may not be conclusive) might be to try the vinegar test against
some unwashed gravel.  I suspect that unless you got a lot of silt in with your
gravel, you probably won't see much of a difference by explicitly leaving it
unwashed, either in carbonate content or in iron content.

David W. Webb
Enterprise Computing Provisioning
Texas Instruments Inc. Dallas, TX USA
(214) 575-3443 (voice)  MSGID:       DAWB
(214) 575-4853 (fax)    Internet:    dwebb at ti_com
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