Parts  One  and  Two  of  Metals  and  koi
were full of facts and figures to give readers
background     information.     They     were
written    so     that     koi     keepers     have
information to hand as a base for decision
making when deciding how to protect their
koi  or  to  solve  some  koi  health  problems.
That’s fine and dandy as far as it goes but,
as a committed koi keeper, I know full well
that it is the practical implications for our
koi which tend to mean the most!
From a practical view W ITHIN A few months of launching our
pond mark four, we were delighted that
we had not experienced green water or
blanketweed.  In  our  ignorance  we  felt  we  had
‘cracked it’ and had achieved the ultimate pond.
Unfortunately  our  koi  did  not  agree  with  us.
Thus our unplanned experiment of the use of zinc
(and  copper)  to  prevent  blanketweed  showed
such intervention has a very serious risk of short,
medium  and  long-term  ill  effects  on  koi  health.
With  pond  mark  five  we  celebrated  pea-green
water and chuckled with pleasure when fringes of
blanketweed  appeared.  I  am  pleased  to  say  our
koi were delighted too!
    As   a   committed   koi   keeper,   I   do   not
understand  putting  koi  at  risk  when  there  are
natural,   or   simple,   methods   of   controlling
blanketweed  which  are  ‘koi’  safe.  Neither  do  I
understand  adding  metals  to  pond  water  which
are known and accepted to harm koi. Why ensure
that  no  harmful  copper  piping  is  used  in  a
recirculation  system  but  then  add  copper  at
above koi ‘safe’ levels to control blanketweed? In
Mr Spock’s famous words, ‘It’s illogical Captain.’
    Let us go back to actual metals damage to fish.
What are the classic symptoms of metals damage
to koi? Although there is a specific damage list,
the degree of damage can vary from very mild to
the ultimate result, death. It all depends on the
amount of metals entering the water. Autopsies
have  revealed  the  presence  of  metals  in  fish
tissues (flesh) after fish have been kept in metals
contaminated water for a sufficient period of time
for the metals to have been laid down.
    The  lower  the  levels  of  metals  entering  the
water the longer it will take for any damage to
occur  or  to  show.  With  one  koi  keeper  it  took
eighteen months for fish health problems to start
appearing  but  metals  damage  had  been  slowly
and insidiously affecting his fish. It could take far
longer. Obviously when higher amounts of metals
enter  the  pond,  fish  damage  will  accordingly
occur  more  rapidly.  Alan  Rogers  showed  this
clearly  in  his  well  known  articles  about  high
Part 3 By  Ann Telford PRACTICALIMPLICATIONS FOR THE KOI KEEPER & Koi Left: The koi delighted in the pea green water of pond
mark five, during the ‘green’ stage, growth rates and
colour development were excellent. Four fish slightly
injured during netting/transfer/emergency vat stages,
all fish self healed without any intervention.