Koi and Goldfish Basics

Koi and Goldfish Basics

So you purchased new koi and goldfish for your ponds, now what??

In this blog, we will go over the bascis of koi and goldfish and how to take care of them. 


Koi fish are ornamental variants of common carp (Cyprinus carpio). Both koi and carps are members of the Cyprinus family, which includes carps, koi, and minnows.

The term koi is derived from the Japanese word for "living jewel".

Farmers kept the colorful cousins of the carp in their rice gardens in the nineteenth century Japan, which is when keeping and breeding began.
Breeding and raising these colorful fish grew popular and is now an increasingly common hobby. Unfortunately, their popularity has led to them becoming invasive in waters throughout the world.

Koi Behavior

Koi are calm fish that will engage with one another. They create schools of between 5 and 15 individuals and swim in highly coordinated formations.
They are an active, free-swimming fish who will display their vivid colors at any opportunity.


In order for koi fish to survive in a pond, a filteration system and water circulation are required. In a stable environment, koi thrive. Large temperature fluctuations can occur in a shallow pond, thus it should be at least 3 feet deep. If you reside in a location with lengthy, cold winters, the pond should be 3 feet or deeper if you intend to overwinter the fish.

Adding steep borders to your pond can discourage predators such as herons and racoons from wading in.

Your pond's pH should be kept between 6.5-8.

The best way to care for koi is to create an ecosystem complete with plants. The following are some of the best plants for a water garden:

  • Water hyacinth: provide coverage as they float on the surface of the water, provide natural filteration; hardy in zones 8 to 10.
  • Water lilies: provide shade, lowering the temperature of the water, soak up any potential harmful heavy metals in the water.
  • Water irises 
  • Mosaic plant
  • Creeping jenny
  • Pickeral
  • So much more

 Recommended Minimum Pond Size 

At least 250 gallons of water are required for goldfish. Your pond should be at least 3-4 feet deep and incorporate both shallow and deeper parts.
When it comes to koi, the general rule is to keep 10 gallons of water for every inch of fish or one 6 inch fish for every 100 gallons of water. For male koi fish, the minimum amount for gallons of water should be 750 gallons. Whereas, the female koi should have a minimum of 1,000 gallons. So plan for at least 1,000 of water. 

What fish or critters are good to interact with koi?

Koi and goldfish get along well. Grass carp are an excellent addition to your pond since they operate as a natural pruning system. They have a voracious appetite for vegetation and can help to tame any plants that are out of control.
Sunfish get along well with all types of carp, and redear sunfish are an excellent option for stocking a carp pond.
Amphibians (particularly frogs) are the best pond companions.
Snails are another fantastic alternative since they eat algae, which keeps the filter from becoming clogged.

Avoid introducing bluegill into your pond because they are natural competitors of any sort of carp or koi and can be harmful to your pond.

Koi and Golfish Care

These fish are noted for their voracious appetites in the wild.
They are omnivores that consume seeds, plant material, algae, zooplankton, and insects.
You should acquire high protein koi food or commercial food. They can be fed up to twice a day. Giving them only what they can consume in 5 minutes.
When you initially purchase them from a fish store or a supplier, they will most likely come in a bag. Before introducing your new pond companions, it is recommended that you quarantine your new fish for at least 2-3 weeks in a separate holding tank.
To learn more about the quarantine process and why it is recommended, click here

If you do not wish to quaratine your fish, float the bag the fish are in for about 10-15 minutes. Depending on the temperature of the day, you don't want to leave them in the bag as the bag acts as a greenhouse and "cook" the fish.

Open the bag after a few mintues to let some pond water in. Once you think the fish have acclimated, open the bag and let your new pond critters explore their new home.