NEWS 115
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There are also long-finned Koi.
A Common Goldfish of the ”Super Red” strain.
substrate suitable for digging,a pH between
6 and 8.5, and a lot of swimming space.
Goldfishes are less demanding as regards
water quality, but can otherwise be treated
as for Koi. Koi and Common Goldfishes are
completely winter-hardy and can be
overwintered at 4 °C, while in summer they
will tolerate up to 30 °C.
Appropriate feeding
Both species are omnivores. Their natural
food consists of small organisms such as
insect larvae, snails, small crustaceans, etc,
plus decaying plant material (detritus) and
soft-leaved aquatic plants.In the aquariumor
garden pond they can readily be fed on all
the usual frozen, live, and dry foods available
in the aquarium hobby.There are also special
foods for both Koi and Goldfishes available in
the pet trade.Dead leaves (autumn leaves) of
native deciduous trees (Beech,fruit trees,Oak,
Alder,Birch,Maple,Walnut,Willow,etc) should
always be available in small quantities as
supplementary food, and will also provide
the fishes with secondary plant substances.
Like almost all fishes they should be fed
several times per day with small portions
that are eaten completely within five
minutes. Both Goldfishes and Koi can do
without food for a number of days (e.g.
during holidays) without problem. At water
temperatures of less than 10 °C they should
not be fed at all.
Correct maintenance
In the aquarium regular large partial water
changes are the most important element of
maintenance.Depending on the population
this can be 50% of the tank volume weekly,
but in tanks with a low population density
can be reduced to 25% every 14 days. The
temperature of the new water should be
roughly in line with that of the tank water,
but up to 5°C temperature difference is
nothing to worry about. The new water
should always be colder, never warmer, than
the aquarium water. Water changes are
impracticable in the garden pond.Koi ponds
require a filtration system,but well designed
Goldfish ponds don't need any equipment.
Aquarium and tankmates
Goldfishes and Koi are slow swimmers with
a moderate need to move around. The
bottom area of a tank for Koi should be
about 8-10 times body length by 4-5 times
body length. The same formula applies to
the basic Goldfish types (Common, Wakin,
Shubunkin, Comet), while the size can be
reduced by about a third for the long-finned
types (Veiltail, Ryukin, Celestial, Pearl Scale,
Bubble-Eye, Oranda).
The depth of the tank will depend on the
space available, but outdoor ponds should
be at least a meter deep to protect the
occupants from frost. Veiltail types are
generally not winter-hardy in central and
northern Europe. The tank decor should be
Spartan: sandy substrate, rounded water-
worn stones, and aquatic plants. In the case
of the Goldfish forms with modified eyes
(Dragon-Eyes, Celestials, Bubble-Eyes)
particular care is required to ensure that the
fishes don't damage their eyes on
decorative objects.
It is best to keep Koi and Goldfishes in
groups though they can be kept singly. The
ratio between the sexes in the group is
unimportant.
Life expectancy
Koi generally live to be 30-40 years old, and
there have been rumors of specimens more
