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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