"Pam Gibbs" wrote in message
...
Lowes didn't have river rock so DS brought home marble chips, which is
white
and pretty, for the veggie filter. Is it OK to use marble in the veggie
filter or is it bad. Someplace I read it will lower make the water too
alkaline? I feel fairly sure that the rocks won't stay pretty and white
for very long, too. Thanks for any advice!


Stolen from Google. [Rod Farlee]

[quote]
No.
Marble is metamorphosed limestone (calcium carbonate) or
dolomite (calcium magnesium carbonate). It dissolves with
atmospheric carbon dioxide to form the bicarbonate.
On average, the world's rivers are saturated with this. Saturation
produces moderate hardness and alkalinity (pH buffering), and is
typically associated with a stable pH of 7.6 to 8.2. All that's good.
Like others here, I used marble gravel in aquaria for years.
[quote]

I have these on my walkway and aside from the PITA of cleaning the leaves
out of them. They are still white. Although the odd piece has rusted.

Just make sure you wash them well, as they are very dusty.