The size to which koi can grow is simply amazing and continues to rise. Jumbos measure at least 30 inches and weigh in at well over 30 lbs. The magical metre mark has also been broken in the gosanke variety
It is a great accomplishment for a koi hobbyist to grow a 4 inch koi into a 2 foot one. It means both a healthy environment and proper care has been provided
On this page we will summarize the fundamental keys required to enable your fish to reach their growth potential. All the factors are key |
Genetics are predetermined physical traits. If a fish does not possess the bloodline to develop into a large specimen, it simply will not despite the keepers diligence. The goal is of course for every fish to reach that size limitation. Most koi will reach an adult size of at least 20 inches if cared for properly
When selecting young koi, try to get a female with a larger head and frame. Knowing the bloodline is critical - large parents mean the chance for a big fish. Of course solid coloured fish such as Ogons, Chagoi and Magoi generally have the potential to grow larger than the more inbreed gosanke varieties
If you want to grow a large fish, you have to start the process from birth. It is critical to put the framework and size on in place in the first 2-3 years and trying to grow a 15 inch 5 year old to 28 inches is not going to happen |
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Water quality is pivotal. Everyone knows, we are water keepers first, fish keepers second . If there are chronic levels of Ammonia and Nitrite present, you will not only hinder growth, but will likely cause a disease state. Excess Nitrates will also slow growth down and pH needs to be stable and oxygen saturation a going concern. Provide chemically clean water and your fish have every chance to grow consistently and quickly
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Mud ponds provide an abundance of natural food with lots of depth and swimming space. The sheer dilution factor alone ensures excellent water quality
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Although koi can adapt to life in lower temperatures, their ultimate growth potential will not be achieved. The optimal SET (standard environmental temperature) is in my opinion about 25-27 degree celsius. This will accelerate the metabolism and allow a tremendous amount of food to be fed
Although there can be a cooling down period for the fish in the Winter months, this period should be short and not extreme. First year fish need to spend Winters in warmer waters or run the risk of being stunted |
Even if you provide all of the above, without proper nutrition, fish will not maximize their growth. Consider 6 or more small meals per day as fish are grazers with less than efficient digestion
Because koi are heavily vegetarian their diet should include dark green leafy vegetables. The key words variety, freshness, nutrient content and frequency all apply |
Obviously the pond dynamics are important. It is not by coincidence that fish put on the best growth in low stocked high water volume mud ponds. These large deep ponds allow fish to exercise and develop their musculature as well as provide lots of natural food. This scenario mimics nature with the added benefit of fish not wasting energy looking for food and just focusing on growth
Although a smaller pond can be made to appear larger by installing jets, it is pretty tough to match the magic of a mud pond |
As mentioned, these items are more like a 1a, 1b, 1c etc list because they are all so important. If you can incorporate all of the keys, there will be a synergistic effect and fish should put on great size quickly
1 year old Tosai can be over 16 inches and in successive years, 4 - 6 inches can be added. As the fish approach 5 years old, growth will slow down but this also depends on the bloodline
I once had a growing contest with one of my friends. We both had 35 gallon tanks and each purchased one 2 inch fish to grow. After 6 months, my fish was almost 8 inches while his was just 3. I attribute this growth to my home made filter, weekly water changes, heating and the live tubifex worms which I fed 3 times a week |
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This shot was taken in the April, a 8-9 inch tosai Shiro Utsuri earmarked for the mud pond |
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By November, the fish has grown considerably. Length and mass have increased and the fish displays great conformation
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The fish was measured at 45 cm (18"). That is an excellent growth rate of over 1 inch per month as the fish grew about 10 inches in just 7 months |
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