I. Recommended Addition Ratios by Stage

1. Tosai (≤1 year old)
   • Not recommended to add body-building feed. This stage should focus on high-protein growth feed (protein ≥40%) to promote skeletal extension and foundational body development.
2. 2-Year-Old Koi
   • Body-building feed can be introduced at 10%–20% of the total feed amount. It is best used during the peak summer and autumn growth seasons (water temperature 23–28°C) and discontinued in winter.
3. 3–4-Year-Old Koi
   • This is a critical period for increasing body thickness. The addition ratio can be raised to 20%–40%. For underweight koi or those with genetic potential for large size, the upper limit can be used short-term.
4. Adult Koi (≥5 years old)
   • To further enhance body fullness, maintain an addition ratio of 20%–30%, but closely monitor liver/kidney function and fat deposition.
     

II. Precautions When Using Body-Building Feed

1. Upper Limit and Duration Control
   • 50% is the safe upper limit, and continuous feeding should not exceed 2 months to avoid metabolic strain.
   • A "pulse feeding" method is recommended: feed body-building feed for 4–6 weeks, then switch to regular feed for 1–2 weeks before repeating the cycle.
2. Water Quality and Oxygen Requirements
   • Body-building feed produces more metabolic waste, so ensure dissolved oxygen ≥6 mg/L and enhance mechanical filtration and regular water changes.
3. Combining Exercise and Body Shape Management
   • Incorporate moderate water flow stimulation (e.g., wave pumps) to promote muscle development rather than mere fat accumulation.
   • Regularly measure the ratio of body length to height to avoid imbalance (e.g., excessive "short-body" appearance) from over-thickening.

III. Adjustments for Special Situations

1. Preparation for Competitions
   • For competition koi, a ratio of 40%–50% can be used in stages during the 3–4 months before a show, but should be supplemented with vitamins (e.g., VC, VE) and digestive enzymes.
2. Low Temperature or Stress Periods
   • When water temperature is below 20°C or koi are in poor condition, pause body-building feed and switch to easily digestible low-temperature feed (e.g., wheat germ-based).
     

IV. Health Risk Warnings

• Excessive strain on the liver and pancreas, leading to fatty liver, dropsy, etc.
• Accelerated water quality deterioration: Significant increase in ammonia from uneaten food and waste.
• Body proportion imbalance: Over-thickened back height with underdeveloped tail stock, affecting swimming coordination.