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Re: Aquatic Plants Digest V4 #1224

Tom Wood wrote:

> Ca (ppm)- 180 ppm TOTAL hardness, which isn't really "soft" per Tropica (see
> below) but seems to work for me.

Tom's comment reminded me that US readers need to use Tropica's hardness
guidelines with caution.  The hardness scale used by Tropica is *way*
different from what is customary in the US.

from Tropica's Website    USGS glossary 
                          (ppm converted to nearest dGH)

Very Soft      < 3 dGH    Soft               < 3 dGH     0-60 ppm
Soft           4-8 dGH    Moderately hard    3-7 dGH   61-120 ppm
Average       9-13 dGH    Hard              7-10 dGH  121-180 ppm
Hard         14-20 dGH    Very Hard          >10 dGH     >180 ppm
Very Hard      >20 dGH

So Tom's water would be "average" by Tropica's standard, but hard to
very hard by US standards.  The tap water at my office carries 8 dGH and
would be soft by Tropica's usage but hard by USGS usage.  Locals call it
hard water.

Roger Miller