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What's the difference between Koi and goldfish?

Koi (Cyprinus carpio) and Goldfish (Carassius auratus) are both in the same family: Cyprinidae.  All Koi have the same body type, but very greatly in color.  They can also grow up to two to three feet in length.  Goldfish are mostly orange in color, with a few types that also have black, white and calico colors.  They come in a wide variety of body shapes, but stay relatively small in size.

How long can Koi live?
Koi usually live around 20 or 30 years.  The oldest Koi on record was named Hanako.  It purportedly lived to be about 226 years old.  It lived in a pond that was in a stable area (read low geologic activity) and was passed down from generation to generation.  Hanako died around 1977.

What kind of food should they eat?
During the summer, when the water temperature is above 60 degrees Fahrenheit, feed your Koi fish a high protein Koi food.  During the fall and spring, when the water temperature is between 52 and 60 degrees Fahrenheit, feed them an easy to digest wheat germ based Koi food.  When the water is below 52 degrees, stop feeding your Koi.

How big do Koi get?
Most domestic Koi usually grow about 12 to 15 inches long.  Japanese Koi usually grow 22 to 26 inches in long.  Jumbo sized Koi grow up to 34 to 36 inches long.

Does the size of the pond hinder a Koi's growth?
The size of a pond will not stop a Koi from growing.  The size of the pond, along with other factors like health, feeding, water temperature and water quality affect the speed of their growth.  A Koi will keep growing until it has reached its genetically predetermined size.

Can Koi and goldfish live together in the same pond?
Yes, Koi can goldfish are both docile and can live together. They can live any species of fish that is considered "docile". They will interbreed and create mix offspring 

I have a filtered, thousand gallon pond, how many Koi can I put in it?
You can put about ten small Koi in it, but as they grow you will need to find new homes for a few. This is the rule of thumb however the amount of fish also depends on the water quality adn filtration capability. 

How many gallons of pond water per Koi fish would you recommend?
We recommend the following GPK (gallons per Koi) rates based on their size:
Small Koi (2" - 8"): 100 - 150 gallons
Medium Koi(8" - 14"): 250 - 300 gallons
Large Koi(14" - 24"): 400 - 500 gallons
Jumbo Koi(24" - 36"): 750 - 900 gallons

The GPK estimates are based on long term housing for the Koi.  Indoor winter tanks can be small, but must accommodate enough room for the Koi to swim around comfortably.

What is the temperature range that Koi can live in?
Koi can live in water that ranges in temperature from 34 degrees F to 90 degrees F.  They won't thrive at the extreme temperatures though.

Can Koi stay in the pond during the wintertime?
They can stay in the pond as long as you keep a hole in the ice with a de-icer.  It allows fresh oxygen to enter the water and carbon dioxide to escape.  Other measures like adding a bubbler near the surface, a backup de-icer (in case the primary one fails) and an aquarium power head to move the water at the surface to keep a larger portion of the pond open will help get them through the winter.  For more information, read our article on
 wintering Koi.

Will big Koi eat smaller Koi?  Can I have mixed sizes in my pond?
Koi are omnivorous and they may eat Koi fry or eggs, but they will leave smaller fish alone.

How much do Koi cost?
Medium, large and jumbo sized Koi are priced on a per fish basis depending on: size, body conformation, skin luster and color.

What's the difference between Domestic, Imported and Japanese Koi?
Domestic Koi are any Koi fish that are bred in the US.  Imported Koi are brought into the US from another country that produces Koi.  Japanese Koi come from Japan and only Japan.  Unscrupulous dealers will call domestic Koi "Japanese" if they came from imported Japanese brood stock but were bred in the US.  Some will also try to pass off "imported" Koi as being superior to domestic, even though they can come from any breeder in any country with no quality control.

Why are Japanese Koi so sought after?
Japan is where the hobby originated and where the standards were set.  Many breeders have been in business for several generations.  The bloodlines the Japanese breeders have cultivated exist nowhere else in the world.  The bloodlines and breeding technique the Japanese use have created quality Koi fish that grow bigger and have better colors than any other breeders in the world. These are the reasons Japanese Koi are so sought after.

What makes for a really good Koi?
Koi are judged on body conformation (no physical defects), color and skin luster.

What was the most expensive Koi sold for?
Grand Champion Koi at the all Japan Koi Show usually sell for six figures.  A few have even sold for seven.

Is it ok to buy Koi from eBay or Craigslist?
We don't recommend buying Koi online due to a disease outbreak in your pond. Howeveer if you do buy online, discuss testing and health with the person that you are buying from.  We quarantine each shipment of Koi in our facility for about a month and we test our Koi.

I'm going on vacation for a couple weeks.  Should I have someone feed my Koi?  How long can they go without me feeding them?
Koi can go a couple weeks without your feeding them during the summer time.  They will eat bugs and will nibble on the algae on the sides of the pond.  You should have someone check on your pond regularly to make sure it is operating correctly and the Koi are alright.

Will my Koi pick on a new one when it it introduced into the pond?
Not at all, Koi are docile and will accept a new addition to the pond with no problems.

Why are most of my Koi bumping and slamming one of the larger ones into the pond walls?
If its spring or early summer, your Koi are spawning.  Spawning is triggered by rapid changes in water temperature.

How often and how much should I feed my Koi fish?
Feed your Koi fish as much food as they will eat in about a couple minutes.  Do this a couple times a day.

My Koi tear apart and eat my pond plants.  Is this normal?
Unfortunately, yes.  Koi are omnivorous and love to eat pond plants, which they find delicious.  Small Koi won't do much damage, but large Koi will uproot your favorite lily.  We suggest cordoning off a section of your pond or even having a separate pond for plants altogether. Also you can buy lily protectors and floating islands for your plants to preotet from the koi. 

Having Koi can be extremely rewarding and relatively care free. They are low maintenance and full of energy, life and color. Any other questions or concerns you have you can bring to the pond clinic and we will help you find answers. We sell Decorative and Select Koi grades in 3 sizes and two varieties: butterfly and straight fin. Goldfish are available as well, we carry sarassas, comets, and shubunkins. 

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A Message from Mark Sousa (A.K.A. Doctor Pond), owner of Action Water Gardens in Tolland, CT

You may ask yourself, "Why choose Action Water Gardens?". The answer is simple. Customer service. As the owner, I am the business. I've been in the landscape and water gardens business for over 15 years. I strive to be knowledgeable about the products and services that we offer and I provide one-on-one consultation on the issues you are facing, whether you are installing for the first time or simply maintaining your current garden or waterfall. See what our customers have to say.

We take pride in our installations. View our photo galleries of the many installations that we've done and judge for yourself. We focus solely on water gardens, ponds, fountainscapes and waterfalls. It's not a sideline of another business, this IS our business.

We service all of Connecticut - including Fairfield County, Hartford County, Litchfield County, Middlesex County, New Haven County, New London County, Tolland County, Windham County - as well as Western Massachusetts - including Worcester County, Hampden County and Berkshire County.

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