Koi Fish Care - Cyprinus rubrofuscus

Published May 13, 2020
Author: Mike - FishLore Admin
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The Koi is a carp that was selectively bred originally in Japan for desirable colors. Japanese Koi can get to be very large with 2 feet plus being a common size for adult fish. Because of their large size these are pond fish and they do best in large outdoor ponds. Each fish needs several hundred gallons of water to adequately care for them. A common mistake is to buy too many fish for your outdoor pond. While young, the volume of water in the pond may be fine, but as these fish grow they will need larger volumes of pond water to prevent growth stunting.

There are many varieties of them available with some fetching ridiculous prices for this pond fish. The names of various types are based on the patterns and colors exhibited by the fish. The Tancho variety is highly sought after having a primarily pure white body with an orange colored pattern on the top of the head. It is a beauty.


People often confuse goldfish and koi. These fish are similar, both being carps, but koi get much larger and have barbels on the sides of the mouth that they use for foraging and finding food. They also have similar care requirements such as feeding and temperature but they need much larger living quarters than goldfish.

The great thing about keeping them is that they can and will develop personalities which makes them great pets. This fish lives for a very long time with a life span of 20 years and likely much longer if cared for properly. Proper care means providing large enough volumes of water, feeding high quality fish foods specifically made for them and keeping the water clean. Clean out the pond filter media often and remove debris from the water surface and the substrate on a regular basis.

Overall, this is a fantastic fish for the properly sized outdoor pond. Keeping them in climates where it drops below freezing or gets above 90 °F (32 °C) for extended periods of time will be difficult due to water temperature issues. If you do live in an area like this, you will need a deeper pond.

Cyprinus rubrofuscus in pond Yellow Cyprinus rubrofuscus Ghost Cyprinus rubrofuscus

Koi Types and Color Variations

Orange and black Ghost Yellow Ghost Cyprinus rubrofuscus Orange black and white

Koi Care Details

Scientific Name : Cyprinus rubrofuscus

Common Names / Types : Common Carp, Leather Carp, there are 26 fixed varieties of Nishikigoi koi.

Bekko - most often a white with black patterns.
Kohaku - a white fish with red patterns. No other colors besides red and white should be present for show quality.
Ogon - sometimes also called a lemon koi, these are usually gold or silver in color.
Taisho Sanke - has three colors, white, red and black.
Tancho - a prized variety that is white with a bit of orange on top of the head.
There are many more types available with more being developed by breeders.

Care Level : Moderate - these fish are quite hardy once established but require very large living quarters in outside backyard ponds.

Size : Can grow to be 36 inches (92 cm) or bigger!

pH : 6.5 - 7.5

Water Temperature : 36°F - 85°F (2°C - 30°C)

Water Hardness : 5° to 15° dH,

Lifespan : Thought to be able to live for 100 years or more - 20 years or more in a backyard pond. The record for longest lived koi is thought to be 200 plus years.

Origin / Habitat : They have been kept in Japan and other parts of Asia for hundreds of years. Other parts of the world have been farm raising this fish for several decades. This is a type of carp.

Temperament / Behavior : They can get quite large and may become more aggressive when ready to breed. Males may chase, bully, bump and pester the females. Smaller fish kept in the pond may become food for the larger fish. Carp are considered an invasive species due to their ability to tolerate a wide range of water parameters.

Breeding / Mating / Reproduction : It can be quite difficult to breed them in a backyard pond since they will eat the eggs. They spawn in late spring / early summer. To successfully breed them you will need to do a couple of things. The first is to have suitable spawning sites in the pond. The second is to prepare them for spawning by feeding them a high quality diet.
Slowly increase the amount of high protein fish foods over a period of several weeks to get them ready. Spawning sites can be a little tricky. The females will look for heavily planted areas to deposit their eggs. Another alternative if you don't have many plants in your pond is to create a spawning mop out of a rock and some yarn. To create a mop, you tie the rock into the center of many long pieces of yarn. The rock is used to sink and hold the yarn. The females will drop the eggs and the males will fertilize them.
Once you have fertilized eggs, they will hatch in about 5 days and you need to have suitable foods ready to feed the babies once they are swimming. Suitable foods would be brine shrimp and other small fry foods. Crushed flakes can be offered after a few weeks.

Pond Size : Because of their large adult size, they need a pond of 1000 gallons (3785 liters) or larger.

Tank Mates : Best kept with conspecifics, maybe the common plecostomus.

Disease / Illness : Freshwater Fish Disease - Diagnose, Symptoms and Treatment - Ick (Ichthyophthirius multifilis) and Costia (Ichthyobodo necator) can be deadly along with secondary fungus infections caused by these parasites. They can also get flukes and worms. Keep their water clean and quarantine new arrivals for several weeks before acclimating them to your pond.

Food : This fish is an omnivore, which means that they will eat both plant and animal matter. For optimum growth and color they need to be fed a high quality and varied diet. It can be easy to overfeed them since they are like little puppy dogs begging for food when they see you. Resist this temptation to keep your pond clean and your fish healthy! There are pellets and flakes that provide a balanced diet and these are recommended for the main portion of their diet. Use caution if using live foods such as feeder guppies or other small fish species since they could introduce disease to your pond. Worms will be relished and can be given to your pond fish occasionally.

Gender : It can be somewhat difficult to determine differences between the genders until they mature. They should be ready to breed around age three. Males may develop small white spots called tubercles around their gill areas when ready to spawn. Females will become larger or more plump when swelling with eggs. Watch for the males to start chasing the females around the pond. It's a good idea to keep more females than males so that the aggression by the males is spread out amongst the various females.

Fish Lore Forum : Koi Forum

Photo Credit : Photos copyright JJPhoto.dk

References : Koi Super Simple Guide

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Koi Comments

From: Samantha - Pond
I have both indoor aquariums and a 1200 gallon outdoor pond in my backyard. I have to admit that the pond is more fun for me than the aquarium and it's the fish in my pond that make it that way. They beg as soon as they see me around the pond. They don't exhibit this behavior when they see my husband because they know who feeds them. I don't get all wrapped up in the show names and show quality stuff. I just like to kick back by the pond, watch the fish and relax while having a frozen drink. Great times. My fish are quite peaceful and don't show any kind of aggressive behavior. Maybe they are not mature enough for breeding. I don't plan on breeding them anyway. I also wanted to warn others about raccoons coming around the pond at night. They will steal and eat your fish!

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