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Re: Aquatic Plants Digest V4 #1165

Robert H. wrote:

> >>Lava rock     -- might be awfully jagged but otherwise it should be fine
> unless it has a whitish calcite coating on it.  Here I  like the cobbles and
> pebbles that have...<<
> I presume they have the same type of lava rock common in every LFS, very
> porous, very light weight, and usually red. You can also get the exact same
> thing as landscape rock. Never seen this type of rock jagged to any extent,
> feather weight..you know what I am talking about Roger?

I believe I know what you're talking about, but certainly not all lava
rock is like that.  I stopped at my LFS on the way home from work just
to make sure.  The lava rock they were selling was black, rough and
mostly jagged.  I few pieces were a little rounded, but even those were
plenty rough enough to damage a startled fish.
Lava is a pretty common stone around here.  It's mostly black basalt in
flows of pahoehoe that can spread for miles and miles in all directions,
but there are lots of different kinds.  What is usually called lava
ranges in density from heavy, solid rock to the spongy texture that you
describe.  The color ranges from pure, glassy black to a strong rusty
red.  The lighter-weight and redder rocks are usually volcanic cinders
and ejecta rather than real lava.  The black, dense rocks come from the
interior of lava flows, and the black, bubbly rocks come from the
surface of the flows.

> I dont know if it is
> dyed red or natural. Looks more like a natural sponge than anything else to
> me...except its dark red.

The rust-red color is natural and probably the result of weathering.

Almost any lava rock is chemically safe for an aquarium; the rare
exceptions are things like carbonatite lava from east Africa or fresh,
acidic ejecta from an active volcanoe.  The only problem with it is that
it can be very rough.  It's great if you can get it smooth enough so it
won't gouge a scared fish that happens to dart into it.  

Roger Miller