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Hardness and plants

A couple of remarks have appeared on this list lately that I fear may be
confusing to tyros.  Some folks have intimated that "hardness" is bad for
plants.  First, I am not an authority on this subject so I used the Tropica
catalog as a reference.  Second, European water is ofter VERY HARD, so when
Europeans say hard they mean something like OK or West Texas.  Where a
teapot lasts a week before it fills up with CaCO3 deposits.  These remarks
also apply to those who are concerned about using a substrate containing
shell fragments for planted tanks.  I will not address the needs of fish
here.  Some fish DO require soft water.

That said, hardness is a blessing.   Hardness comes in two kinds, permanent
and temporary.  Chemists, forgive me, I know this is obsolete terminology.
 But I am trying to deal with whatever folks may conceive hardness to be.   

Permanent hardness is ordinarily a sign of calcium in the water (sometimes
Magnesium).   Both of these are essential plant nutrients and used in
significant quantities.  Calcium and sulfur are sometimes called the "other

Temporary hardness is permanent hardness plus transient hardness.
Transient hardness is often due to CO2, another serious nutritional
requirement of plants.  It is not necessarily bad.

Going thru the Tropica catalog, I found only two plants that will not
tolerate what Tropica calls "average" hardness (which is about 150-200ppm
in most of Europe, I would guess).  They are the rare Eusteralis stellata
and our old "buddy" Glossostigma elantoides.  And there are folks who will
tell you Glosso requires hard water.   So go figure.

Please don't spend a lot of money, time and energy fooling around with your
water unless you KNOW you need it.  It is more likely to cause harm than good.

Dave Gomberg, San Francisco            mailto:gomberg at wcf_com