Think of a bottle of medicine for
upset stomachs. Standing in the
cupboard the medicine divides out into
a clear coloured liquid at the top and
opaque ‘sludgy’ stuff at the bottom of
the bottle. The sludgy stuff consists of
undissolved particles. Shake the bottle
thoroughly and the two things combine
to form an opaque mixture through the
whole of the bottle. The ‘sludge’ hasn’t
dissolved, it has mixed in with the clear
liquid to form a ‘suspension’. The
‘sludge’ is the equivalent of metals
particles in water, i.e. the part of the
metal in suspension.
For a clear liquid to be coloured
but to remain clear, something has
been dissolved in it. These dissolved
substances, are now called a solution.
This is similar to the second form of a
metal found in water, the dissolved part.
Apart from iron particles coating fish
gills in hard water, it is the ‘dissolved’
metal, i.e. the part of the metal in
solution, which is more harmful to koi.
The amount of each metal in particle
or dissolved form varies depending
upon the type of water the metal is in.
See Figure One above.
So there are two forms of each heavy
metal in the water, they each need to be
‘reduced’ differently.
SOME ALTERNATIVE
PURIFICATION MEDIA ON
THE MARKET:
Pre-filters, Carbon and Ceramic Blocks:
PROS: They trap ‘particles’ of metals,
sand etc. Linking this with Figure One,
if tested on hard water, an activated
carbon block or pre-filter could be rated
to reduce about 60% of heavy metals.
The only heavy metals this rating applies
to, is the reduction of particles of
metals, i.e. the undissolved metals,
which are sometimes referred to as a
suspended metal.
CONS: They do not reduce dissolved
metals.
Activated Carbons (block or granular):
PROS: They are cheap and readily
available. They reduce chlorines
and pesticides.
CONS: They do not reduce dissolved
metals. In the filtration (purification)
industry it is accepted that if an
activated carbon temporarily
collects a dissolved metal such as
zinc, it then ‘dumps’ it back into
the treated water.
NOTE: Some activated carbon block
cartridges are mixed with an extra
substance to reduce dissolved lead.
However, apart from a house with old
lead plumbing, lead in UK tap water is
now so low that lead on its own is not
generally a problem for UK koi.
Ion-Exchange Resins:
The dissolved form of metals in general
can be a problem for koi health, either
in a minor or a major way. It all
depends upon the quantity of a single
metal or the total metals in individual
tap waters.
The fish world mainly relies on ion
exchange resins to reduce dissolved
metals. These resins exchange one ion
for another. It is a bit like throwing a
pink jumper out of a drawer to make
room for a blue one. Different resins
reduce different substances e.g. metals,
nitrate or some soften water.
PROS: Reducing dissolved metals can
be very beneficial to koi.
CONS: Great care has to be taken
choosing resins. Some resins ‘throw
away’ substances which are actively
dangerous to koi, e.g. acids.
Any brine refreshable resin throws
away a salt-based substance as it softens
water or collects nitrates – this is usually
Sodium Chloride. There is a potential
risk that the discarded substance could
react with some medications such as the
Formaldehyde part of Formalin and
Potassium Permanganate. Koi cannot
tolerate uncontrolled amounts of
Chlorides. They should not be kept
permanently in a ‘brine’, that is a
‘salt’ solution.
Brine refreshable water softening
resins are not allowed to be installed on
drinking water systems for us and
should be seen as unsuitable for koi.
The right purifier has to be chosen to
protect koi.
Domestic Purifiers
PROS: They treat water in the home so
it is pleasant for ‘people’ to drink. They
tend to change the smell, colour and
taste of water, sometimes they soften
water as well. CONS: Domestic
purifiers can contain 1
8 K O I
C A R P A N N
T E L F O R D
FIGURE ONE WATER
TYPE AMOUNT
OF METALS IN PARTICLE FORM (SUSPENSION)
AMOUNT OF METALS IN DISSOLVED FORM
(SOLUTION) Hard
Water About two
thirds About one
third Water that
is neither About
50% About 50%
soft nor hard
Soft Water About
one third About
two thirds Many
things can contribute to koi ill
health and death. Mr Brian Batty lost 47
koi. At that time he used zinc and copper
to control the blanketweed. Mr Batty had
the courage to build another koi pond
and now controls the blanketweed in a
different way. Today he has a pond of
healthy koi which he can enjoy. CASE
STUDY TWO Photos
supplied Brian Batty