Koi (Cyprinus carpio)
With many types on aquaponic fish available you must put
some thought into the purpose of the fish. Some fish are raised in aquaponics
for the purpose of eating, and some simply just to correlate with the plants.
Koi are not considered a good fish for eating, so for those looking to harvest
not only plants, but fish as well from your aquaponics system might be better
off with a different fish such as Tilapia, Catfish, Bluegill or a crustacean
such as the RedClaw Crayfish or Prawns. You don’t have to incorporate edible
fish in your aquaponics systems. Vegetarians or those who prefer not to harvest
their own animals may want to consider Koi.
The word "koi" comes from Japanese, simply meaning
"carp". It includes both the dull grey fish and the brightly colored
varieties. What are known as koi in English are referred to more specifically
as nishikigoi in Japan (literally meaning "brocaded carp"). In
Japanese, koi is a homophone for another word that means "affection"
or "love"; koi are therefore symbols of love and friendship in Japan.
Koi are one of the most popular fish used in aquaponics due
to their long-life span, they easily live and breed within your system, and have
a strong resistance to diseases, parasites and their attractive colors. Koi are
omnivorous fish which means they will eat just about any food you give them. They
will eat algae, debris, and plant matter that fall into their pond/tank, so in
many cases, additional feeding is not necessary. You can also feed them peas,
lettuce and watermelon.
Koi are a colored form of Amur carp (Cyprinus rubrofuscus)
that are kept for decorative purposes in outdoor koi ponds or water gardens. They
are a cold-water fish, and their ability to survive and adapt to many climates
and water conditions has aloud them to work well with aquaponics. The length of
a koi can average up to about 3.28 feet. However, Koi can reach lengths of up
to 2ft after 4-5 years if water quality and space in the tank are
optimized. On average, they grow about 2
centimeters per month, and have a lifespan of 25 – 35 years. The common carp is a hardy fish, and koi
retain that durability. Koi are cold-water fish, but benefit from being kept in
the (59–77 °F) range, and do not react well to long, cold, winter temperatures.
In general, Koi can function in temperatures ranging from 35 to 85 degrees.
Feeding is not recommended when the water temperature drops
below (50 °F). Care should be taken by
hobbyists that proper oxygenation, pH stabilization, and off-gassing occur over
the winter in small ponds, so they do not perish. Their appetites do not come
back until the water becomes warm in the spring.
Like most fish, Koi reproduce through spawning in which a
female lays a vast number of eggs and one or more males fertilize them. Nurturing
the resulting offspring (referred to as "fry") is a tricky and
tedious job. They produce thousands of offspring from a single spawning. When Koi
naturally breed on their own they tend to spawn in the spring and summer
seasons. The male will start following the female, swimming right behind her
and nudging her. After the female Koi releases her eggs they sink to the bottom
of the pond and stay there. A sticky outer shell around the eggs helps keep
them in place so they does not float around. Although the female can produce
many spawns, many of the fry do not survive due to being eaten by others. On
average if the egg survives around 4-7 days the fry will be hatched from the