By Seng Tran, CCKS Member (Past Board Member and President)
There are three main factors to consider and maximize your koi growth:
- Genetics Potential
- Water Quality
- Quality Koi Food
GENETIC POTENTIAL
Genetics is one of the main factors in growth potential for koi. Starting with koi that are known for good growth potential goes a long way. You can choose koi varieties, bloodlines, and koi sourced from farms known for growth. Even if these items are unknown, you can inspect young koi for these items to help maximize growth:
- Body Mass, Bone Structure
- Body Proportion
- Aggressive Eater
WATER QUALITY
Good water quality is essential to koi health and maximizing growth. Ensure your koi pond equipment offers good:
- Filtration System
- Waste Removal System
- Biological Filtration System
Pond Water Turnover Rate
Pay close attention to your pond water turnover rate per hour. Ideally, you should have 100% of your pond water filtered at least every 2 hours. If your pond water turnover rate is one or more times every hour, your koi fish will likely be healthier and grow larger.
Koi Fish Load Density
The koi fish load density, or the number of koi in your pond in comparison to the size of your pond, can be a factor in good koi growth. If you have too many fish in your pond, it can impact the water quality and competition for food.
Regular Water Changes
To maintain good water quality, do a minimum of 10% water change weekly. The maximum water change should be 100% weekly. Always test your water parameters before and after water changes to track the water quality and ensure it is in healthy ranges for your koi.
Plentiful Oxygen
Ensure your koi always have plentiful oxygen, especially depending on your fish load. Added bubblers in addition to your waterfall can be necessary to maintain koi health, especially when trying to grow them larger.
QUALITY KOI FOOD
Choose good or high-quality ingredients in your koi good. High protein and good ingredients assist in koi health and growth. During the koi growing season, feed your koi 5-10 times per day to maximize growth. However, each feeding should be a small quantity that can be eaten within 5 minutes or less.
Most Koi Growth Happens in First Five (5) Years
For maximum growth, ensure to follow these guidelines in the first five (5) years of the koi’s life. After 5 years, koi growth usually slows down and eventually stops. See the charts below for Good Growth Rates compared to Average Growth Rates of Koi in the first 5 years.
KOI GROWTH CHART – GOOD GROWTH
| START SIZE (inches) | GROWTH (inches) | GROWTH % | END SIZE (inches) | |
| Year 1 | 0.25 | 9.75 | 4000% | 10 |
| Year 2 | 10 | 10 | 100% | 20 |
| Year 3 | 20 | 6 | 30% | 26 |
| Year 4 | 26 | 4 | 15% | 30 |
| Year 5 | 30 | 2 | 7% | 32 |
KOI GROWTH CHART – AVERAGE GROWTH (50% LESS THAN GOOD GROWTH)
| START SIZE (inches) | GROWTH (inches) | GROWTH % | END SIZE (inches) | |
| Year 1 | 0.25 | 9.75 | 4000% | 10 |
| Year 2 | 10 | 5 | 50% | 15 |
| Year 3 | 15 | 2.25 | 15% | 17.25 |
| Year 4 | 17.25 | 1.3 | 8% | 18.5 |
| Year 5 | 18.5 | 0.6 | 3% | 19 |