Language of Koi | Back to Basics Q&A

large koi Ben Cornford

Impressively large koi can make for years of enjoyment in a backyard pond. The gray Soragoi in the middle was approximately 36 inches when Ben Cornford took its picture at Blackwater Creek Koi Farms.

What are some of the biggest hurdles to selling and keeping ornamental pond fish? Knowledge, space, time and cost, just to name a few. Offering some honest answers to common questions may help increase koi enjoyment — and sales!

Many of the questions we are asked may seem simple or even trivial, but remember, you were new to this wonderful hobby at one point yourself. Empowering people with the knowledge they need can lead to meaningful relationships, which can increase sales. Here are some of the most common questions I have answered over the years.

How big do koi get?

On average, koi can grow to 24 inches, although in large ponds with adequate food and time, they can grow to 36 inches or more.

How fast do they grow?

Warmer water temperatures increase growth rates. Water temperatures consistently above 70 degrees can encourage growth of 1 inch per month. Quality feed will provide the nutrition they need to thrive and grow.

How big of a pond do I need?

Remember the simple days of a goldfish in a glass bowl? The pond size you should start with is completely up to you. Smaller koi and goldfish can do well in larger aquariums, a rain barrel-sized container or a small, preformed pond. You can get started fairly simply. As you advance your love of fish keeping, you may wish to upgrade to a larger, more elaborate pond setup. Larger fish require larger ponds, but as I like to say, koi are pigs with fins — they do not need ultra-clear water. They can be very happy and thrive in a dirt-bottom farm pond and learn to greet you at the pond bank for food. The real question is, what do you want as an outcome of ornamental fish keeping?

Are they expensive?

aeration methods

Numerous methods of aeration can be employed to help with gas exchange, including floating heaters, bubblers and even Styrofoam rings, depending on the outside temperatures.

No; some very nice fish of almost every color can be bought for less than $10. Your budget and tastes will dictate what is best for you. I typically recommend you start with lower-cost fish over 6 inches to start out. As you fall in love with the fish and realize how simple keeping them can be, you may come back for some higher-priced fish and gear.

What kind of equipment do I need?

You really don’t need much. A preformed pond in partial shade will happily hold some fish. With that said, you may wish to have a larger, more elaborate setup right away with a pump, filtration and more. Typically, the bigger the pond, the easier it is to manage. There are many, many options, depending on your comfort level.

What about winter?

Koi and goldfish are very resilient fish and can live under the ice. Fall preparation and cleaning of the pond helps. Ponds with large groups of fish may require more preparation and aeration for gas exchange. When you get to that point in the hobby, we can help you out.

How often do I feed them?

water bag koi

Large fish are typically moved in water and a bag to reduce the possibility of injury.

It depends on the situation. In a lightly stocked farm pond, you may only need to feed the fish for enjoyment. In a more highly stocked pond with little natural food availability, once to twice a day will do it. One of the most enjoyable aspects of fish keeping is when your fish greet you at the pond edge, and you get to feed them and enjoy them up close.

How do you tell boys from girls?

When fish reach 12 inches or longer, it’s easier to tell the boys from the girls, especially is late spring and early summer. Girls will be more rounded in their midsection, as they will be carrying tens of thousands of eggs. A more scientific approach is to flip a fish over and look underneath. The vent areas look slightly different. If you are buying fish over 12 inches, most fish sellers can give you a fairly accurate prediction of girl or boy.

Will they have babies?

When late-spring light levels increase and the pond temperature approaches a consistent 70 degrees, the fish will be looking to lay eggs. Koi lay thousands and thousands of eggs, all in hopes of just a few surviving. With so many eggs hatching, these baby fish require a lot of food, and thus only a few typically survive in a hobby pond. You can breed koi, but it requires a special setup and preparation.

What about the fish with long fins?

koi no teeth

No, they don’t bite. Koi do not have teeth as we know it. This makes for great times hand-feeding — or soaking your toes in the pond!

Are they koi? Yes, they are. Just as koi are carp, longfin or butterfly koi have been selectively bred for these traits, with their origins going back to Japanese koi breeders.

What fish should I buy?

It all depends on your needs, budget and comfort level. Start with a few fish, and let’s talk in a couple of weeks about getting you some more.

How do I keep them healthy?

Koi and goldfish are naturally very strong fish. Keeping them healthy is as easy as providing a good environment and adequate food. A single goldfish can thrive in a gallon bowl of water if the water is kept clean and the fish is fed each day. The same is true for any sized pond. And to add to that, a pond filled with green water can be very, very healthy.

What is the difference between imported fish and those raised in America?

There is no difference. If a Japanese woman has a child in America, is it different? No, it is not. Fish of all qualities and varieties are commonly grown and sold all over the world.

Why should I have a pond and keep fish?

Sitting next to a pond and watching the fish swim around and look for food can be one of the most calming experiences. Water falling over a waterfall while sun glistens off the surface allows you to slow down a bit and enjoy. Think of it as living art that continues to surprise and enlighten every day.

Being new to the ornamental fish hobby should be an exciting and rewarding experience. Providing honest answers to simple questions will help introduce a lifestyle that many of us already enjoy and love. Take the time, share your knowledge and prepare to be rewarded in so many ways.

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