How to introduce new fish to a pond
Fish are the natural addition to any pond and often the reason for adding water to the garden. For fish to thrive and give you years of pleasure there are a few guidelines to follow.
Can I put fish straight into a new pond?
It may not be ideal to put fish directly into a new pond. This is due to several factors that can affect their overall health and well-being.
When a pond is first established, it undergoes a process called the nitrogen cycle. This is crucial for creating a stable environment in which beneficial bacteria can thrive. These bacteria break down harmful ammonia produced by fish waste into less toxic substances, such as nitrites and then nitrates.
In a new pond, this beneficial bacteria is not yet established. Introducing fish too soon can lead to an ammonia buildup, putting the fish at risk. For this reason, it’s generally recommended to wait a few before introducing fish to your pond.
Here are a few tips for adding new fish to your pond:
Starting a new pond

After setting up your pond with a pump and filter, make sure to add Fresh Start when you fill the pool. With the filter running (you can run your fountain or waterfall at this stage), leave it all to settle for at least 24 hours to ensure everything is working correctly and allow the water temperature to stabilise.
Only introduce one or two fish at the start. The trick is to increase fish quantity slowly over a period of three months to allow the life support system to mature. After three months, by which time the life support system will be mature, fish feeding can be gradually increased, and the frequency of the partial water changes reduced. You will now have a healthy, matured pool.
Careful attention in these early weeks will pay for itself in an easy to maintain, and healthy home for your fish.
Buying and taking them home
Always choose healthy, strong looking fish from a good aquatic retailer. Ensure they are a species suitable for the size of your pond.
When you have purchased your fish you should take them straight home, gently transporting them in a shaded bag as fish are less stressed in the dark. Find out more information on how many fish you can keep in your pond.
Settling them in
When you get home float the sealed bag in the pond (out of direct sunlight) for 20 minutes. This is to equalise the temperature of the bag water to the pond water. Doing this avoids shocking the fish with different water temperatures.
Open the top of the bag and roll down the sides to create a floating bag.
Add a bit of the pond water to the bag every 5 minutes for a further 20 minutes. This allows the fish to acclimatise to the water chemistry of the pond.
After a total of 30-40 minutes slowly tip up the bag and pour the fish into the pond. Make sure no fish are caught in the corners.
Feeding
Because of the shock of moving home, the fish may hide for a day or two, you may not want to feed them during this period. After one or two days try adding a little food. They will soon get used to their new home and become familiar with the feeding routine and be waiting for you at the surface when they see you approach. Find out more about feeding your here.
Make sure you have a good pond filter that can clean up any uneaten food which could potentially harm your water parameters.
Monitoring water quality
As your new fish settle in, it’s crucial to monitor the pond’s water quality. Newly established ponds may experience fluctuations in pH and ammonia levels due to the recent introduction of fish and other aquatic life. To ensure your fish thrive, regular testing should be part of your routine.
pH
With pH levels aim for a pH between 6.5 and 8.5, which is suitable for most pond fish. Sudden spikes or drops in pH can stress or harm fish, so be sure to test often.
Ammonia and nitrite
Newly set ponds can exhibit high levels of ammonia and nitrite, particularly before the nitrogen cycle has been fully established. Ammonia should be kept below 0.02 mg/L, and nitrite levels should similarly stay at a safe minimum.
These compounds are highly toxic to fish, so consider buying a good water testing kit and performing weekly tests during the first month.
Nitrate levels
Once the biological filtration begins to kick in, you may see nitrate levels rising. Nitrates should ideally be kept under 40 mg/L, as elevated levels can lead to algae blooms and poor water quality.
Temperature
Fish are sensitive to temperature changes. Generally, water temperatures for pond fish should be kept between 20 and 25 degrees celsius. Monitor the temperature daily during the first few weeks after adding fish to your pond. Sudden fluctuations can cause stress and even lead to illness.
To help maintain a stable temperature, make sure that your pond has some shade, especially during the hottest parts of the day. If conditions change significantly consider using a heater or air pump to control temperatures.