Comments
Koi are very nice fish for a pond. They will usually grow too big for most aquariums. But it's enjoyable to start them off in an aquarium, where they can be easily seen, and later before they grow too big for an aquarium, carefully acclimate them to a pond at a time of year that the temperature of the water in the pond is within 2 degrees of the temperature of the water in their aquarium, so they will not be shocked by the change in water temperature.

Appropriate Home
An outdoor pond or a large cool water aquarium with at least 50 gallons of water, an external power filter with a BIO-Wheel, and at most 1/4 of gravel, but no heater because Koi are cool water fish. Click here for more about cool water aquariums. Click here for more about ponds.

Recommended Diet
Floating food labeled for Goldfish and not labeled for Tropical Fish. Several brands of goldfish food are available in most stores that sell fish for ponds. Floating pellet foods are very good for larger pond fish and are also available in most stores that sell fish for ponds.

We have read advice elsewhere that all goldfish and Koi should be fed sinking food, because when fish take food off the surface of the water, they will swallow air bubbles that will cause problems. This is contrary to our experience.

I just watched my goldfish eat off the surface. After most mouthfuls of food, he burped a bubble of air out his gill. The ancestors of this fish have been eating food off the surface of the water for a very long time. Of course they also ate off the bottom and at all levels of the water between the top and bottom too.

So don't worry about your goldfish or Koi swallowing air while eating. Feeding food that floats is a good practice. If your fish don't eat all of the food in 10 minutes, get a net and remove the uneaten food. Click here for more about feeding.

I also feed Koi a few live Black Worms. I feed each Koi two or three Black Worms every other day. Click here for more about Black Worms.

Compatibility
Koi are usually kept with other Koi. Regular Koi will sometimes nip on the slower swimming Butterfly Koi. So, if you keep them together, be sure the Butterfly Koi are not being nipped and annoyed by the Koi. Koi can also be kept with Pond Comets and Shubunkins, but not with Fantails, Orandas, or Telescopes, which swim slower, are less aggressive, and are not compatible with Pond Comets and Koi. Click here to read more about several groups of compatible fish.