Bringing home a new koi is one of the most exciting moments in pond keeping. But the journey from a breeder or farm to your pond is stressful for fish — and how you handle the transition can make all the difference between a thriving fish and a struggling one.
At Crystal Creek Koi Farm, we want every fish we send home to thrive. That starts with proper acclimation. Here’s our complete guide to getting it right.
Why Acclimation Matters
Koi are highly sensitive to changes in water chemistry and temperature. Even small differences between the water in a shipping bag and your pond — in pH, temperature, ammonia, or dissolved oxygen — can cause osmotic shock, immune suppression, and stress-related illness. A slow, careful transition gives your fish time to adjust and dramatically improves survival and long-term health.
What You’ll Need
- A clean bucket or quarantine tank
- A thermometer
- An air stone and small air pump (recommended)
- Your pond water test kit
- Dechlorinator/water conditioner
Step 1: Float the Bag — Don’t Open It Yet
If your koi arrived in a sealed bag, place the unopened bag on the surface of your pond or quarantine tank for 15–20 minutes. This allows the water temperature inside the bag to gradually equalize with your pond, preventing thermal shock. Resist the urge to open it early — this step is critical.
Step 2: Test Your Water
While the bag is floating, test your pond water for pH, ammonia, nitrite, and temperature. If the values are significantly different from typical shipping water (which tends to be lower pH and higher ammonia due to fish waste in transit), you’ll want to take extra time during the next step.
Step 3: Slowly Add Pond Water to the Bag
Open the bag and roll the top down to create a floating collar. Every 5–10 minutes, add a small cup of your pond water to the bag. Continue this for 30–45 minutes until the bag water volume has roughly doubled. This gradually introduces your pond’s chemistry to the fish, allowing it to adjust without shock.
Step 4: Transfer the Fish — Not the Water
Use a soft mesh net or wet hands to gently transfer the koi into your pond or quarantine tank. Do not pour the bag water into your pond. Shipping water can contain elevated ammonia, bacteria, and pathogens from transport that you don’t want introduced to your pond ecosystem.
Step 5: Monitor for 24–48 Hours
Keep a close eye on your new koi for the first couple of days. Some hiding or shy behavior is completely normal. Watch for signs of stress or illness:
- Rapid gill movement
- Flashing (rubbing against surfaces)
- Lethargy or staying near the surface
- Loss of appetite
Hold off on feeding for the first 24 hours to reduce ammonia load while your fish settles in.
Should You Quarantine First?
If you have existing koi or pond fish, the answer is yes — always quarantine first. Even a healthy-looking fish can carry parasites or disease that are invisible to the naked eye. Introducing an unquarantined fish directly into an established pond puts your entire collection at risk.
We recommend a 2–4 week quarantine in a separate tank before introducing any new fish to your main pond. For a full breakdown of how to set up and run a quarantine tank, read our Importance of Quarantine guide.
Quick Tips for a Smooth Transition
- Acclimate during cooler parts of the day to avoid heat stress.
- Keep the area calm — minimize noise and foot traffic near the pond.
- Make sure your pond filtration is mature and cycled before adding new fish.
- Don’t add too many new fish at once — it can spike ammonia levels.
- If your koi was shipped, work efficiently once the bag is opened as ammonia builds quickly.
We’re Here to Help
At Crystal Creek Koi Farm, we’re committed to your success as a koi keeper. If your new fish shows signs of persistent distress — labored breathing, visible lesions, loss of balance, or refusal to eat after several days — don’t hesitate to reach out to us. We’re happy to help troubleshoot and get your fish back on track.
Happy ponding! 🐟