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Re: calcium silicate

On Sun, 13 Feb 2000, Steve Pushak wrote:

> When inquiring at the hydroponics store about calcium carbonate (which
> they don't stock) they told me they have calcium silicate. How soluble
> is this? is it a useful form of calcium supplementation for the planted
> aquarium?

The only natural calcium silicate I know of is the mineral wollastonite
(CaSiO3), which is more properly called calcium metasilicate.  A quick
tour through a web search engine turned up many references to calcium
silicate, most of which seemed to refer to CaSiO3.  There are also a few
references to di- and tri- calcium silicates and a few other variations.
There are enough different applications for calcium silicate that I have
to wonder if they're all talking about the same thing.

Anyway, CaSiO3 is unreactive and insoluble, but it may be used as a
carrier for other chemicals, and some form of calcium silicate is used as
to keep other powdered chemicals free-flowing -- perhaps that's the use
that the hydroponics supplier sells it for.

If they do have some form of soluble calcium silicate, then I'd probably
avoid it like the plague.  The silicate that you would be adding along
with the calcium isn't toxic in any way (to the best of my knowledge).  
It may promote diatom growth if their growth in your tank is
silica-limited.  Probably more importantly, it can cause "hard-water"
deposits from hell.

I have a lot of silica in my tap water and the resulting deposits can't be
removed with any sort of usual cleaner or mineral stain remover.  The only
way I've found (so far) to get them off is to polish them off.

Roger Miller