NEWS105
24
ow is hardnessmeasured?
Nowadays this is nobigdeal. First of
all, you can obtain the figures from the
watercompany that suppliesyou.However,
water companies produce drinking rather
than aquarium water and sometimes the
ladies and gentlemen there can be a bit
curtorevenchurlishwhenaquaristsphone.
So it is rather more practical to be able to
findoutthetotalandcarbonatehardness in
theaquarium for yourself.
Very easy: test strips
It is possible tobuy test strips,whichoften
even indicate several water parameters
H
In the first part of this serieswe introduced you to the chemical basis of
what is termed the “hardness” of water. If you havemisplaced the issue
(News 104) and are unable to refer to the article, that is not a major
disaster.The printed edition of News 104 is sold out, but youwill find all
theback issues of theNews in PDF form at
they
canbedownloaded freeof charge.
But nowback tohardness…
That’shardness for
you!
Part2
byHeikoBlessin
simultaneously. They are simply dipped in
the water sample to be tested in order to
obtain a measurement. These test strips
have small test areas that contain
chemicals.Thecolorationof these testareas
indicates the result of themeasurement –
they turn pink, red, blue, or green
depending on the test in question. Drop
tests are significantlymoreprecise,but test
strips are very popular for obtaining a
guidelinemeasurement.
Drop tests
Thecommonesttypeoftest isthedroptest.
Inthiscaseacolored liquid (indicator liquid)
is added to a precisely measured water
sampleand thenanother liquid (aso-called
chelating agent or reagent) is added drop
bydropuntil suddenly thecolorchanges.In
the GH Test from JBL, for example, from
brightredtobrightgreen.Thehardnesscan
be calculated from the number of drops
required to bring about the color change,
with one drop of reagent usually
corresponding to 1°dGH. Drop tests are
very simple to perform, requiring only a
single vial in which the indicator and
reagent canbebrought together.But these
single-vial testsdon’tworkverywell invery
soft water (less than 3° dGH), as the color
change takes place almost immediately
and isunnoticeableas the indicatordoesn’t
become brightly colored enough from the
addition of just one or two drops of
reagent. In such cases you know that you
have very soft water, but you don’t know
how soft.You then requirea testwhere the
indicator and reagent are added to
separate vials. The amount of water is
simply increased tenfoldand ten times the
amount of indicator is added, and reagent
addeddropbydropuntil thecolorchanges,
but this time eachdrop represents 1/10of
the actual hardness indicated by the
reagent.Thuswhere, for example,onedrop
of reagent normally representsonedegree
of hardness, in the diluted water test one
drop of reagent represents only 0.1 of a
degree. In this way you canmake precise
measurements invery softwateraswell.
Water Chemistry
Rainbowfishbiotope inAustralia. All photos:Hans J.Mayland
