Do phosphates and heavy metals bind to silicate based sand?

[HighlandReefer]

I don't believe they do? :)

[Randy Holmes-Farley]

Not to nearly the extent they will to calcium carbonate. But organics will coat most anything, and those organics may contain metals and phosphorus. :)

[HighlandReefer]

Thanks Randy. Another plus for using silica based sands. Maybe someone will come up with a silicate based porous rock for use in reef systems. :)

I am also curious if the silica based sands clump like the argonite sand does?

[therealfatman]

Pumice. It is volcanic rock and is commonly sold for high prices in pet stores. A pumice based concrete mix is even sold, that is a mixture of pumice agregate and Portland Cement.
http://www.toolbase.org/Technology-Inventory/Foundations/pumice-crete
Pumice is a type of extrusive volcanic rock, produced when lava with a very high content of water and gases (together these are called volatiles) is extruded (or thrown out of) a volcano. As the gas bubbles escape from the lava, it becomes frothy. When this lava cools and hardens, the result is a very light rock material filled with tiny bubbles of gas. Pumice is the only rock that floats on water, although it will eventually become waterlogged and sink. It is usually light-colored, indicating that it is a volcanic rock high in silica content and low in iron and magnesium, a type usually classed as rhyolite. If the lava hardens quickly with few volatiles, the resulting rock is volcanic glass, or obsidian. Pumice and obsidian are often found together.

[kaskiles]

<a href=showthread.php?s=&postid=14304508#post14304508 target=_blank>Originally posted</a> by HighlandReefer
...Maybe someone will come up with a silicate based porous rock for use in reef systems. :) ...

Someone came up with an aluminosilicate based reef rock:
http://www.reefcentral.com/forums/showthread.php?s=&threadid=1562112

They just haven't made shapes that would look nice as tank aquascape.

I've just thrown one in my sump a couple weeks ago, and in a couple more I'm going to remove my live rock. I'm starting to wonder though, is this aluminosilicate block any better (for bacteria and zooplankton housing) than a filter sponge of the same dimensions...