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Re: rain water

>From: Patrick <perk at cisco_com>

>the KH (12) & GH (14) of my tap water are too high, I looked at reserve
>osmose equipment but this looks like an expensive methode - not to
>mention the waste of water (only 1/4 ratio)
>what about just using rain water (collected via the roof of the house &
>stored in a 7000 l concrete 'barrel')
>I live in Europe, Brussels, and am worried about pollution.
>rain water :
>PH : 7.8
>GH : 3
>KH : 2   (I would have expected lower)
>would it be sufficient to run that rain water trough a activated carbon
>filter before use ?  Buying water at the local shop is not an option due
>to the size (700l) of my tank.

The high (for rain water) pH, GH and KH values are most likely from the
concrete barrel.  I don't have my chemistry book with me, but I vaguely
recall that calcium sulfate is a major constituent of concrete.  I think
that calcium hydroxide, which picks up CO2 and becomes calcium carbonate,
is in concrete, too.

Before worrying about pollution, I would try out the water with guppies, or
some other relatively cheap fish, or just some invertebrates.  It probably
will turn out to be fine.  The main problem with pollution is acid rain,
and it looks like that isn't a problem for you.  For continued plant
growth, you will probably have to add some potassium and magnesium.

Paul Krombholz, in mild Central Mississippi, with rain on the way.