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
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
By Ann Telford
PRACTICALIMPLICATIONS FOR THE KOI KEEPER
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.