aluminium sulphate levels suddenly entering his
own pond. (For tap water treatment, aluminium
sulphate  should  be  seen  as  a  mix  of  particulate
and dissolved aluminium.)
     Sudden influents of very high metals can cause
complete   pond   wipe-outs.   The   higher   the
pedigree  the  more  likely  it  is  that  the  koi  will
succumb to metals damage. Young fish tend to be
more  susceptible  to  metals  than  older,  mature
fish.  Eg.  A  sudden  metals  influx  to  the  pond  is
likely  to  cause  more  deaths  among  the  younger
fish than among the adult fish.
    Metals  levels  vary  so  much  in  UK  tap  water
that  some  tap  water  may  not  need  any  metals
reduction  while  other  tap  water  supplies  will
need radical intervention to keep koi alive. One of
the  worse  examples  I  saw  was  a  dealer  who
quoted  loosing  £8,000  of  koi  stock  to  very  high
levels of copper, for fish, in their tap water. At the
other end of the scale, there are some tap water
supplies  where  metals  are  so  low  I  daren’t
tell our koi about them or we’d be moving
and building yet another pond!
     It is impossible to lay down rules
about    the     need     for     metals
intervention    because    of    this
tremendous    variation    in    the
amount of metals to be found in
water. It is possible to say that if
you have fish health problems an
underlying   cause   may   be   the
amount  of  metals  in  the  pond
water and metals effects are one
of the first things which should be
considered   when   investigating
such events.
    So what do you look for? At last,
cry    those    who    thought    this
information would never come! As it
is so rare, let’s not over emphasise the
horror  of  suddenly  finding  a  pond  of
dead koi.
    Classic  symptoms  of   metals  damage   are:
Lethargy,  lack  of  interest  in  feeding,  loss  of
colour, damaged fins, raised scales, red ‘irritation’
patches on the skin. As the damage increases; gill
damage,  difficulty  or  failure  to  wound  heal,
ulceration and bacterial invasion. Sometimes it is
possible to see mucous stripping, certainly metals
can  lay  fish  open  to  parasitic  invasion.  As  skin
and  scale  are   damaged  sometimes   koi  may
develop  fungus.  Long-term  and  more  insidious
are damage to internal organs such as the liver,
kidney and reproductive organs. Growth can also
be suppressed.
    You  can  see  from  the  list  of  health  problems
how easy it would be in some cases to treat
the  symptoms  and  miss  finding  the
underlying  cause.  It  is  generally
accepted  today  that  parasites
and  bacteria  should   be
identified  before
Right: Fast growing plants grown hydroponically
(no soil) in marsh garden give attractive, natural
and fish safe control of nitrates and phosphates, therefore
the water is algae/blanketweed free without
the use of ‘metals’ or other chemicals.