How to grow Jumbo Koi?
Like humans, Koi use energy for growth and maintenance. The energy used for maintenance is not available for growth. So, the less energy they use for maintenance, more energy they can use for growth. The energy used for maintenance depends on the following factors.

  • Water temperature: Koi need less energy as water temperature declines because their metabolic rate is reduced. In high water temperature, their metabolic rate is high. So they need more energy. But they also eat more.
    We bring our koi indoors in the first week of October and keep them at 68*F entire winter. We return them in spring when the water temperature is a steady 68*F. We discovered that the Koi that are left in the pond for winter, take about one month to recover from winter stress and thus lose a full month’s growth in summer. They are also prone to infections rest of the season because their immune system doesn’t work efficiently until June and then they use up energy to grow. The koi that stayed at 68*F in winter not only grew bigger but were also robust due to lack of stress.
  • Water flow: Energy used for physical activities such as swimming and jumping is not available for growth. In the wild, carp live in slow moving rivers. So, if Koi are placed in a pond with high turnover rate or has too many water returns and waterfalls, they will use most of their energy to swim against the strong current which would otherwise be used for growth. So, the flow should be just enough to give them exercise without stress.
    Our pond was about 10,000 gallons. We had a 12ft tall waterfall with about 6000gph water gushing 4ft wide. We also had a 90ft x 2ft long stream that was oxygenating the pond at 2000gph. But we had a single bottom drain and no water returns or TPRs. Some areas of the pond had strong current but some didn't. Our koi exercised when they went under the waterfall or stream return but relaxed when they didn't. Large waterfall does help them rid of parasites.
  • Fear: Koi get stressed if there are predators. Always keep your pond netted unless your pond is 8ft+ deep. If Koi stay in the bottom or hide when the caretakers/visitors come near the pond, they are under constant stress. The stress caused by lack of trust in people is the same as that of Blue heron showing up near the pond. As far as koi are concerned both pick them up from the pond! In such a situation, Koi are constantly using energy to prepare for a flight rather than for growth. When they expect danger, they produce Epinephrine, a hormone that releases glucose into blood (so they can swim faster) and raises their blood pressure. High glucose levels combined with high blood pressure reduce their appetite and thus their growth.
    Our koi trust us so much that even at midnight if I dip my hand in their pond, they kiss my hand. So, play with your koi for 10-15 minutes daily. Touch them; stroke their heads before feeding them. Call them out as you approach the pond so they recognize your voice. Your voice should relieve their stress not cause stress. Our 2 year old Koi are 18”-24” long and 5 year old Koi are 32”-38” long.
  • Music: Koi love instrumental music -music without many highs and lows- Chinese, Japanese, Indian, Middle Eastern. Latin American and ambient/airport/elevator music. They do not like vocals because they cannot see the singer but hear a stranger's voice. Female koi love string music but baby Koi and male Koi love drums and brass (energetic music). When they are indoors in winter, we turn on music at 9am and stop at night. They know not only the sequence of songs but also have favorites. Just before the favorite song begins, they eagerly move about under the speaker. Music drowns all other noise that might startle them (like furnace coming on, strangers talking, and people walking up and down the stairs, opening/closing doors). If you sing their names when they are in stress, you will see them calm down instantly.
  • Busy-ness: Koi in the wild, graze/explore all of their waking hours. The food they find in natural ponds is not nutritious enough if they consume only 1% of their body weight. Besides they are not sure whether they will get any food for their next meal. So, they constantly feed on anything they find. In a hobbyist pond, the situation is exactly opposite. Most of the time, just one meal a day is sufficient for their activities as well as growth. Since hobbyists cannot provide food all day and most ponds don't have plants and rocks, koi lay idle, bored and depressed. This situation can lead to health problems.
    Solution: Plant bog plants with good root structure. Plant roots host algae and bacteria. These will attract zoo-plankton that Koi love. In our pond, we have Lotus, waterlilies, Iris, Grasses etc. We never have to search for our koi. They are always at the top pulling some plants, exploring the iris and other bog plants. So, the key is to make sure your koi have no stress and keep them busy by placing plants with good root structure.

How much to feed?

Available Koi literature suggests feeding 1% - 5% of koi body weight. Some ask you to feed however much they can eat in 5 minutes. Every pond is different; every koi is different. The amount you should feed depends mainly on your water quality, Koi health and age.

Factors that influence Koi appetite:

  • Water quality: Koi ask for food as soon as you do a water change,. Fresh water always increases their appetite. They also look for food when it rains. In the wild, rain brings silt and new food into the rivers. So, they expect the same in ponds.
    Water can hold only limited amount of gas and suspended particles. The more amount koi excrete the less oxygen the water can hold. They release gases like carbon dioxide, methane and hydrogen sulfide and metabolic end products such as ammonia, feces and hormones. They also shed mucus, scales and teeth from time to time. Some of these products are in the dissolved form (ammonia, carbon dioxide, hormones) and others stay suspended (feces) or fall to the bottom of the pond. The dissolved and suspended particles reduce the amount of oxygen dissolved in water. Low amount of metabolic products increase the amount of oxygen available for koi. Products like ammonia, feces and organic materials like rotting  plant matter, attract microorganisms that use these products as food. Such microorganisms use up oxygen to to digest these particles.
    Example: We used to overwinter our Koi in the basement in 12-ft above ground pools. The pools were overstocked. About 200lb koi in a 2400g pool, at 68*F in winter. Each koi had about 12 gallons of water! This is way below the recommended 500gallon/per fish rule. So, we made 25% change daily.

    After we built a 33,000 gallon indoor 4-season pond, we make only 1% change per week if the temperature is under 75*F. If the temperature is above 75*F, we change 2% a week. We use the pond water to irrigate our plants and trees. How often one should change depends on how dirty the pond gets. If you have installed good number of filters, you don't have to change as often. If you feed a lot, you need to make frequent water changes. When koi spawn, you must make a large change. If you have large number of female koi you may have to make multiple changes.
  • Health: Koi in good health can digest high protein food but if the Koi isn’t doing too well or recovering from illness, you should give low-protein food.
  • Age: Koi growth rate is very high in the first 3 years. They need a lot of food during those years. In the first year, Koi are carnivores- eating micro-organisms commonly found in the pond. In the second year, they start nibbling on plant roots. From 3rd year onwards they eat anything that fits into their mouth.
  • Gender: Females need more food than males. Females pass on their carotenoids to their eggs (to make vitamin A). So, they are less colorful and may need more color supplement.
  • Season: Spring-summer is growing season for all things living. In the growing season, Koi eat more.
  • Frequency: There is no evidence of peristalisis movement in Koi gut (food getting pushed forward by contraction muscles. So, the fresh food pushes the old undigested food. This explains why koi excrete 6-12 hours after eating. That doesn’t mean they take 6-12 hours for digestion. It takes that long for the undigested food to travel through the gut. Also, Koi like to eat in the night when no predators are around. You will observe this phenomenon if you have a On Demand feeder. If possible, feed sinking wheatgerm pellets in the night.
  • Amount at a time: We feed 0.5% per day in summer and 0.25% per day in winter which we divide into 3 times. However, they also get daily treats. Our pond offers some food. Fish under 3 years eat a lot and eat very fast. If you mix large Koi with smaller koi, large ones do not get enough food. In addition, large koi sacrifice their share for the young ones because they can survive without food for several weeks without compromising their growth. In such situations reducing frequency to feed more at a time is a better idea.
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