There Is Phosphate In Aragonite Sand

[tmz]

BTW, for those interested in reading the whole Millero article, here's a link to the full text.

Thanks for the link. Seems right on point. I've scanned it;will take more time with it later.

 

[Dan_P]

Silica sand:

The above is from this article by Randy Holmes-Farley:

http://www.advancedaquarist.com/2003/1/aafeature1

Thanks much for this information! The silica dissolution discussion is very interesting. I especially like the surprising observation about its slow dissolution rate.

 

[Dan_P]

Silica sand:

This:

"....In the first experiment I took 3 cups of sand, and suspended it in 3 gallons of freshly made Instant Ocean salt mix that initially contained less than 0.8 mM of silica (0.05 ppm SiO₂). After 48 hours of gentle stirring with a powerhead (the water was stirring, but not the sand), the silica concentration had risen to 17 mM (1.0 ppm SiO₂).
I then rinsed the same sand 5 times with 1 gallon RO/DI water (1 minute each time), discarded the contents, and then ran the same stirring experiment with 2 new gallons of Instant Ocean salt mix. In 48 hours the silica concentration had again risen, this time to 15 mM (0.92 ppm SiO₂). Then I let it sit unstirred for another 96 hours, and the concentration had risen more, to 23 mM (1.4 ppm SiO₂).
In a different experiment, I took about 45 pounds of sand, and added 2 gallons of Instant Ocean salt mix. I let this mixture sit for 7 days, with once a day mixing with my hands for about 30 seconds. At then end of this test, the concentration was 90 mM (5.4 ppm SiO₂).

The fact that silicon dioxide dissolves extremely slowly, as Randy points out that is why beach exdon't dissolve, should make you wonder why silicate concentrations increased so quickly in these experiments. Randy provides a rationale for his observations which seem reasonable.

So warning. The above quote is taken out of context. Until beach sand is tested by itself as well as with organic acids, we still have little evidence that in an aquarium beach sand can be a significant source of silicate. Having said this, I should go check the silicate levels in my aquarium which contains beach sand!

Thanks again for article. It was chock full of information.

 

[tmz]

I did wonder about why beach sand wouldn't dissolve but Randy's rationale . Dissolution from acids linked to organics and/ or other minerals dissolving in fractured mined sand vs beach sand which likely already dissolved to a more stable state satisfied me.

You are welcome. Thought you'd enjoy it.

 

[bertoni]

I suspect silica sand will dissolve, but at a very slow rate. The bacteria inside the sandbed can do some interesting things. I know that they can dissolve calcium carbonate sand, and I thought that they could work the same way with silica sand, but I'm forgetting where I was reading about the issue.

 

[tmz]

Jonathan.

I think this ,also from Randy's article, says so:

A final comment on quartz sand is that it is known that organic acids can increase the rate of dissolution of quartz by at least a factor of ten.39 This may be especially applicable in reef tanks, where organic materials may be in abundance, particularly when organisms are living directly on the sand, potentially releasing such acids directly onto the sand surface.

1. The dissolution of quartz in dilute aqueous solutions of organic acids at 25°C. Bennett, P. C.; Melcer, M. E.; Siegel, D. I.; Hassett, J. P. Dep. Geol., Syracuse Univ., Syracuse, NY, USA. Geochim. Cosmochim. Acta (1988), 52(6), 1521-30.

Above is the refernce per his footnote.

 

[bertoni]

Yes, but I thought I had read another paper that showed the flux rate for an actual sandbed, as I saw for calcium carbonate, at one point.

 

[tmz]

I don't recall that one. I'll look around tomorrow.