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Re: Re: Rocks for the aquarium

>>I found Robert's info on rocks very interesting but have a question.  I
been considering adding some slate to my tank.  I haven't already since you
couldn't see it though the green water!!  Anyway, it is black slate with
deposits of rust-red in places. You can rub it off with your finger.  The
"deposits"  grow in the aquarium and easily crumble into a mess if you rub
across them in the water.  It is obviously not toxic due to the fact that I
used some of this slate for years in African cichlid tanks and it affected
neither them nor their fry.  You do not want to let it rest against glass
though, it won't come off glass if it rests against it for any length of
Is it iron oxide?  Will it have any kind of detrimental/beneficial effect in
a planted tank? It is high light, CO2 injected etc. (the tank, not the oxide
he, he)<<

I dont claim to be anything close to a geologist, but after reading
everything I could get my hands on of this subject for the last three
months, your observation makes sense to me. Slate is a metamorphic
sedimantary rock formed from shale made of mostly clay and fine particles.
Iron oxide is a big part of it, and its not unsual for slate not to be
uniformily one color or texture. It sounds like an oxide of some sort to me.

The main concern of aquarists putting rock into their aquarium is how it
will affect pH. How the mineral content will affect the water I think is of
little concern, but I am not a chemist either. So perhaps Jamie or someone
could comment if iron oxide, zinc, copper or other minerals in rocks could
be made available to plants in either a beneficial or detrimental way. My
feeling is no. No more than lateric rock alone can increase iron levels in
water.  Even the iron oxide in Flourite and laterite can not be used by
plants until bacteria makes it soluable, (Fe+2).

Robert Paul H
Plants, rock, and wood
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