firebrick safe for fish?

can anyone advise if firebricks are safe for fish ponds? i made a pond with a one foot deep plant shelf, but my plants need to be up a little higher in the water. i put the flower pots on old firebricks i had laying around the yard. i waws wondering if they are made of anything that would leech out and harm the fish. Any thoughts on this?
Tony
sorry if this is a duplicate post, am having trouble posting today...
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what are fire bricks? you might want to ask on rec.ponds. Ingrid

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On Fri, 28 May 2004 13:46:11 GMT, "Tony Rivas"

Put a brick in a 5 gallon bucket of pond water and add a feeder goldfish. If the fish is still alive after 5 days, your bricks are safe to use.
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On Fri, 28 May 2004 13:46:11 GMT, "Tony Rivas"

Should not hurt a thing. Fire brick are normally made of alumina cement instead of portland cement. Once fired and cured its no different than any other brick is, other than its ability to take more heat. Visit my website: http://www.frugalmachinist.com Opinions expressed are those of my wifes, I had no input whatsoever. Remove "nospam" from email addy.
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On Sat, 29 May 2004 02:35:00 GMT, snipped-for-privacy@hotmail.com (Roy) wrote:

Fire bricks are made out of clay, not cement. A higher firing clay that usually has more alumina than than the clay used in regular bricks, but clay never the less.
deg
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On Sat, 29 May 2004 03:46:47 GMT, Dewitt

Really? Would you like to put some money on that? NOT all fire brick is made of clay by any means, and even the clay ones use aluimina cement as a binder. Perhaps in days of old when knights were bold and aluminina cement was not invented, they may have used all clay, but since about the 50's or so they ghot aluminima cement or depending on the rating and class of fire brick could have portland or other types of high early cememnts as well. I stated they use alumina cement as a binder to hold the ingredients together, not the sole ingredient. Common percentage is 70% grog, 20% fire clay and 10% alumina for the standard fire brick commonly found in a household fireplace.
Visit my website: http://www.frugalmachinist.com Opinions expressed are those of my wifes, I had no input whatsoever. Remove "nospam" from email addy.
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On Sat, 29 May 2004 21:31:14 GMT, snipped-for-privacy@hotmail.com (Roy) wrote:

We're well off the gardening path, but alumina is not the same thing as alumina cement. Alumina is added to the mix you note above to make the brick more refractory, not to act as a binder. Grog is basically ground up, previously fired brick.
According to http://tinyurl.com/2vajl the main ingredient in alumina cement is monocalciumaluminate. Since calcium acts as a flux (i.e.acts to make ceramic materials melt), I would expect it to be avoided in firebricks. Portland cement has even more calcium so I would expect it to be avoided for the same reason.
I do a bit of pottery and have a number of books on the subject. Several give recipes for firebricks and none show any sort of cement as an ingredient. I'd be interested in any references you can provide that show cement is an ingredient in firebricks.
deg
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On Fri, 28 May 2004 13:46:11 GMT, "Tony Rivas"

If it's High Fire brick, fired at cone 10 or higher, 2500f + it should be vitrified, and therefore should not be transferring much into the water. Any silica in it would have melted, and most of the other ingredients would be bound up in the melted silica aka sand.. it melts and pretty much becomes "glass" and binds the other ingredients together.
But when in doubt, find out from the Brick (usually have the manufacturer name stamped into them..on high fire brick). You can also ask where you bought the brick for the manufacturer's name and maybe even get the phone number. Or find a web page and e-mail address and call them or e-mail them and find out what cone (temperature) the bricks are fired to, and if there would be any chemicals that could leach out into water and harm your fish.
Overall though, they should be ok as long as high fire brick. The lower fire bricks.. would be more likely to leach things out. And bricks in general, some I've even seen crumble after a few years..as they're low fire earthenware, nearly adobe which is just dried in the sun! Others are like Rocks, literally, melted together and not going to change no longer how long you soak them.
Janice
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