Sudden food changes disrupt gut bacteria balance. Symptoms range from refusal-to-eat to swim bladder issues. Transition slowly.
The 7-Day Mix
Days 1–2: 75% old food, 25% new. Days 3–4: 50/50. Days 5–6: 25% old, 75% new. Day 7+: full new food. Smoother for koi.
Watch for Refusal
Some koi reject new food even after correct introduction. Try a smaller pellet size of the new brand; texture matters as much as flavor.
Seasonal Switch is Different
Wheat germ to high-protein when temperature crosses 65°F is intentional. Follow the same 7-day mix but on calendar trigger.
Document the Switch
Note the change date and which fish reacted. Helps diagnose future issues that may trace back to the diet change.