I. Recommended Addition Ratios by Stage

1. Tosai (≤1 year old)
   • The recommended addition ratio is approximately 40% of the total feed amount. At this stage, growth feed should be the main component, supplemented with color-enhancing feed, with a focus on ensuring skeletal development and foundational health.
2. 2–4-Year-Old Koi (Prime Color-Enhancing Period)
   • During this stage, koi pigment cells are highly active. The color-enhancing feed ratio can be increased to 50%–60%, particularly during the suitable summer and autumn water temperature period (22–28°C), to deepen the development of red (Hi) and black (Sumi) patterns.
3. Adult Koi (≥5 years old)
   • The addition ratio can be adjusted to 40%–50%, focusing on maintaining color vibrancy and preventing pigment fading due to slowed metabolism.
     

II. Precautions When Using Color-Enhancing Feed

1. Synergy with Water Quality and Lighting
   • Color-enhancing feed works best under good lighting (natural light or full-spectrum artificial light) and slightly alkaline water conditions (pH 7.0–7.5). Avoid high-ratio use in turbid or low-pH water.
2. Phased Feeding Strategy
   • A "pulse feeding" method is recommended: feed color-enhancing feed for 4–6 weeks, then switch to regular feed for 2–3 weeks to prevent excessive pigment deposition, which can lead to stiff coloration or liver strain.
3. Adjustments Based on Variety
   • For varieties like Kohaku and Taisho Sanke, which emphasize red patterns, focus on feeds rich in astaxanthin or spirulina.
   • For Sumi-focused varieties like Showa and Shiro Utsuri, combine with water quality management (e.g., maintaining temperatures at 15–18°C during colder periods) to stabilize Sumi development.
     

III. Special Applications

1. Preparation for Competitions
   • For competition koi, the color-enhancing feed ratio can be increased to 60%–70% during the 3–4 months before a show, supplemented with vitamin E and carotenoids to enhance color saturation and skin luster.
2. Low Temperature or Stress Periods
   • When water temperature is below 18°C or koi are in poor condition, reduce the color-enhancing feed ratio to below 20% to avoid metabolic strain due to reduced digestion.
     

IV. Health Risk Warnings

• Increased liver burden: Pigment metabolism relies on liver function; overuse can cause fatty liver.
• Water eutrophication: Unabsorbed pigment components can accelerate algae growth.
• Unnatural coloration: Red patterns may become overly dark red, or Sumi may develop a bluish tint, losing natural depth and gradation.