How To Add Fish To A Fish Pond The Safest Way

How Soon Can You Put Fish In A New Pond?

How to stock a new koi pond

If you’ve just gone through the Maryland pond construction process or are in the process of doing so, you’re likely wondering how to stock it with these beautiful fish.

In this article, we’ll walk you through the basics of how to stock a new koi pond and prepare the water for your fish’s arrival.

By the end of this article, you’ll feel confident about being able to successfully (and safely) add fish to your fish pond.

Overview: Prep & Fish Introduction To A New Fish Pond

Koi swimming in a koi pond
  1. Ensure Pond Readiness: Verify the pond is properly sized, has a functional filtration system, and is adequately aerated to support fish life.
  2. Start a Bacteria Colony: Add beneficial bacteria to the pond to initiate the nitrogen cycle, which is crucial for converting harmful waste products into less toxic forms.
  3. Test Water Parameters: Check the pond’s pH, ammonia, nitrite, and nitrate levels to ensure they are within safe ranges for the fish you intend to add.
  4. Acclimate Fish to Temperature: Float the fish in their bags on the pond surface for 30 minutes to equalize the water temperature between the bag and the pond.
  5. Introduce Pond Water to Fish Bag: Gradually add small amounts of pond water to the bag every 5 minutes over a period of 15-20 minutes to help fish adjust to the new water chemistry.
  6. Gently Release the Fish: Carefully net the fish from the bag and release them into the fish pond, avoiding pouring bag water into the pond to prevent potential contaminants.
  7. Observe Fish Behavior: Watch the fish for any signs of stress or discomfort following their introduction, which could indicate issues with water quality or temperature.
  8. Continue to Monitor Water Quality: Regularly test the water parameters in the days following the introduction, making any necessary adjustments to maintain a stable environment for your new fish.

How To Stock A New Koi Pond And Prepare The Pond Water

Koi in tub during koi pond cleaning

Here are some tips for how you can ready your pond’s water for your new koi fish.

Overall Pond Readiness

Creating a fish pond in Columbia, Maryland, that’s both beautiful and sustainable requires thoughtful preparation. Before you add koi or any fish to your pond, ensuring it’s ready to support them is crucial. A well-prepared pond means healthier fish and less maintenance in the long run.

Size and Depth: First, assess the size and depth of your pond. Koi, for example, can grow quite large and need plenty of space to thrive. A depth of at least 3 feet is recommended, especially in areas like Columbia, Maryland, where winter temperatures can drop, allowing fish to find warmer water at the bottom.

Filtration System: A robust filtration system is essential for maintaining water quality. The right filter will handle the bioload of your fish, keeping the water clean and clear. This is where accessories for your fish pond, including various filter types, come into play. Ensure your system matches the size and needs of your pond in Columbia, Maryland.

Aeration: Proper aeration is crucial for oxygenating the water. This can be achieved through water features like waterfalls or fountains or with aerators. A well-oxygenated pond supports healthy fish and beneficial bacteria.

Water Quality: Test your pond’s water for pH, ammonia, nitrite, and nitrate levels. Ideal conditions will vary slightly, but generally, a neutral pH of around 7 is best for koi ponds and fish ponds in general. Adjustments may be necessary to ensure the water chemistry is within safe parameters for your fish.

Predator Protection


You don’t want to go through the process of how to stock a new koi pond just to have predators take your fish. Herons, raccoons, and other wildlife can start preying on your fish. You can put a stop to it.

Some preventative measures for a fish pond include fish caves and tunnels, decoys, and nets. They sure beat sitting outside with a pellet gun all day and night.


Any experienced fish keeper will tell you that filtration is one of the most important aspects of keeping a healthy koi pond. Koi are particularly sensitive to water quality, and even small changes leading to poor water quality can lead to disease.

A good filtration system helps to remove debris and waste from the water, keeping it clean and clear. Filters also help to aerate the water, providing vital oxygen for the fish.

There are a variety of different filtration systems available on the market for a fish pond of any size, so it’s important to do some research to find the one that best suits your needs. This involves knowing how many fish you’ll have in your pond and how much water your pond holds.

Add Aeration

Your fish need to breathe, too!

You aerate a pond by adding oxygen to the water. This makes sure there is enough air in the water for the fish to breathe. Aeration happens naturally when something disturbs the water, such as rain or a waterfall.

However, owning your own fish pond comes with the benefit of man-made aeration. Aerators are an artificial method of adding air to water and are also great for creating a hole in the ice during winter.

Most pond owners place aerators in these areas of their pond:

But even if your fish can breathe, the water still needs to be right, too.

Proper Pond Water PH Balance

The process for how to stock a new koi pond involves preparing the water’s chemistry. Would you find it comfortable if the air was too dry or if there wasn’t enough oxygen? Well, for fish, water is like our air.

You can make sure your fish live healthily and well with proper water pH.

pH measures how basic or acidic something is. Lifeguards do it for pools; we do it for ponds.

A pH of 7 is perfect for fish ponds as it is a neutral pH, like the water we drink. A fish’s blood pH level is about 7.4, so any water pH between 6.5 – 9 is okay as long as it doesn’t vary too often.

Water Temperature

New goldfish pond with bench and stream and waterfall

When it comes to how to stock a new koi pond, the water temperature is one of the most important considerations. Koi are cold-blooded fish, and their body temperature is directly affected by the temperature of the water they swim in.

In general, koi prefer water that is between 65 and 75 degrees Fahrenheit. However, they can also tolerate a wide range of temperatures, from 50 to 85 degrees. The key is to make sure that there are no sudden fluctuations in temperature in your fish pond, as this can cause stress and even death.

As the weather starts to cool off in the fall, it’s important to take steps to ensure that your koi pond is winter-ready.

Start A Bacteria Colony In Your Fish Pond

In the Elkridge neighborhood of Baltimore, Maryland, pond enthusiasts understand the importance of a balanced ecosystem. Starting a beneficial bacteria colony is a critical step in this process. These bacteria are essential for breaking down fish waste, converting it into less harmful substances.

Use a Starter Culture: Purchase beneficial bacteria designed for fish pond use and introduce it according to package instructions. These products are readily available at a reasonable price, making them an accessible option for pond owners in Baltimore, Maryland.

Feed the Bacteria: Adding small amounts of fish food can help feed the bacteria before introducing your fish. This step accelerates the establishment of a healthy bacterial colony.

Patience is Key: Establishing a bacteria colony takes time, typically a few weeks. Monitoring water parameters during this period is crucial to ensure the colony is developing correctly.

Incorporating Plants For A Healthy Ecosystem

In the Towson area, adding native Maryland aquatic plants to your fish pond not only enhances its beauty but also contributes significantly to the ecosystem’s health. Plants play various roles:

  • Oxygenating Plants: Submerged plants like Elodea work tirelessly to oxygenate the pond, which is crucial for fish health and the prevention of algae growth.
  • Shelter and Shade: Floating plants, such as water lilies, offer shade on sunny days, keeping the water temperature consistent and providing hiding spots for fish.
  • Natural Filtration: Marginal plants, positioned at the pond’s edge, naturally filter the water by absorbing excess nutrients, which could otherwise fuel unwanted algae growth.

Introducing Koi Fish To A New Pond

Part of knowing how to stock a new koi pond is actually introducing the fish to the water.

You should wait at least 72 hours before putting fish in your new pond, even if only the water is new. This way, the water temperature and chemistry can level out. Drastic changes in either can have a serious impact on the health of your fish.

You won’t be able to just place them in once the wait is over, though.

After the minimum 72-hour waiting period, here is how you can best put pond fish in your new pond:

  1. Put your fish in bags with an open top (like the kind you get from the fair)
  2. Take the bag and put it in your new pond with the top sticking out of the water. This way, the temperatures of the water equalize, making it easier for your fish to be put in new water
  3. During the next 15 minutes, slowly let some pond water into the bag to get them used to the water
  4. Let them out

Post-Introduction Care

After introducing koi to your fish pond in the Silver Spring area of Maryland, close monitoring and ongoing care are essential to maintain a balanced ecosystem.

Regular Testing: Continue testing the water regularly for pH, ammonia, nitrites, and nitrates. Adjustments may be needed to maintain optimal water quality.

Observation: Keep an eye on your fish for any signs of stress or illness. Active fish that are eating point to healthy fish.

Gradual Additions: If adding more fish, do so gradually to avoid overwhelming the ecosystem. This careful approach ensures the pond remains a healthy environment for all inhabitants.

Do Not Overfeed Fish: Overfeeding fish can lead to uneaten food decomposing in your fish pond, which deteriorates water quality and can harm both fish and bacteria. Stick to the recommended amount of food, ensuring it’s consumed within a few minutes.

What Not To Do When Introducing Fish To New Pond Water

No sign

When introducing fish to new fish pond water in the Columbia, Maryland area, certain practices should be avoided to ensure the health and longevity of your fish.

Can I Put Fish Straight Into A New Pond?

The answer is no, as this can severely impact their health and safety. New water is not the same, chemically or temperature-wise, as their old pond water. Being put into water that isn’t the same as they are used to can cause them to go into shock, illness, or death.

Avoid Using Water From Another Pond

Introducing water from another pond can bring parasites and diseases into your pristine environment. Always fill your pond with treated tap water or rainwater collected in the area. Be sure to clean the water before adding fish!

Avoid Rapid Changes

Sudden changes in water temperature or chemistry can stress your fish, leading to health issues. Gradually acclimate fish to their new environment, especially during the initial introduction phase.

How Long Does It Take Koi To Adjust To A New Pond?

happy koi in a well maintained koi pond

After stocking a new koi pond, it can take your koi fish a few days to a few weeks to fully adjust to their new home. Factors for this timeline include fish size, pond substrate, and if you add other fish at the same time. They need to explore their new home and realize that it’s a safe place.

How Long Do You Leave Tap Water Before Adding Fish To A Fish Pond?


Allow the water temperature and chemistry to settle for about 3 days. The water will run through the filter and get rid of all the chemicals in the water that koi fish can’t tolerate well. Beneficial bacteria colonies will grow and help clean the water as well.

Rules For Stocking Koi Ponds

A good starting point is 1 inch of koi for every 10 gallons of water. It’s better for your koi to have more room than less. This way, they can be comfortable and healthy without straining your pond’s filters or plumbing. Too many fish will lead to health problems.

You may find rules for how to stock a new koi pond that can allow you to have higher numbers of fish. Just consider where the rules come from first. Commercial fish pond operations can have higher inches of fish per 10 gallons because they have the equipment to handle it. Their fish may not be as happy either, being crammed together like that.

If you aren’t sure, feel free to contact a koi pond professional who can help you.

Don’t forget to look into the cost of koi fish.

What Fish To Add To Your Fish Pond

When selecting fish for your pond in Columbia, Maryland, it’s essential to choose species that will thrive in the local environment.

  • Koi and Goldfish: These are popular choices for their hardiness and vibrant colors. They require space to grow and a pond well-equipped with the right accessories to support their health.
  • Native Fish: Consider adding native fish that are accustomed to the local climate of Maryland. These species are often more resilient and can contribute to a balanced pond ecosystem.

What To Know About Koi Fish Before Adding Them To Your Fish Pond

Closeup of koi fish in a backyard koi pond

Is Keeping Koi Fish Easy?

Yes and no. Koi are definitely easier to care for than most other types of fish, but they still require some effort on your part. Koi are hardy fish and can tolerate a wide range of water conditions, but for optimal health, they should be kept in water that is clean and well-oxygenated. Koi also produce a lot of fish waste, so you’ll need to have a filtration system in place to keep the water clean.

Best Pond Size For Koi Fish

You can’t know how to stock a new koi pond without considering pond size. For best results, your fish pond should be at least 10 feet long and at least 3 feet deep. However, if you don’t have the space for a pond that large, don’t worry; koi can also do well in smaller ponds as long as they have enough room to swim around and plenty of hiding places.

Best Water Conditions For Koi Fish

Koi are very tolerant of different water conditions, but for optimal health, they should be kept in water that is clear and has a pH between 6.5 and 9. The water should be well-oxygenated and free of ammonia and nitrites.

Are Koi Fish Okay In Cold Temperatures?


Koi are cold-water fish and can tolerate temperatures as low as 40 degrees Fahrenheit. They will go into hibernation when the water gets to around 40 degrees. If your fish pond is deep enough, it’s okay to let the water freeze over as long as you use an aerator or de-icer to keep a hole in the ice. There are other ways to help your koi fish survive winter, too.

Should A Koi Pond Have Plants? 

Yes! Plants are not only aesthetically pleasing but also provide many benefits for your koi pond. Plants help keep your fish pond water clean by absorbing nitrates and other pollutants, providing shelter for your koi from predators (like herons), and helping to oxygenate the water. Your koi can also snack on them.

What To Feed Koi Fish

Before knowing how to stock a new koi pond, you’ll want to know what koi fish can and can’t eat. Koi are omnivorous and will eat just about anything from commercial pellets to vegetables like lettuce or peas. You can even feed them live food like worms or small insects! It’s important not to overfeed your koi, though. Only give them as much food as they can eat in 5 minutes or so. 

How To Protect Outdoor Koi Fish

If you want to keep your outdoor koi safe from predators like herons or raccoons, there are a few things you can do: install a fence around your fish pond, use netting over the top of your pond, or put a wire mesh screen over any openings leading into the pond.

How Long Do Koi Fish Live?

Koi have an average lifespan of 20-30 years, but some individual fish have been known to live for over 100 years!

Caring For Fish During A Pond Renovation Or Cleaning

Man removing koi fish from tub to pond

The process for how to stock a new koi pond can also apply to a pond with new water. You’ll need to take your koi fish out of the pond during a renovation and any cleanings. Here’s the proper process for it:

  1. Fill a tub with some of the pond water and put it in a shady area
  2. Drain your fish pond of water to make catching the fish easier
  3. Catch your fish with a net and put them into the tub
  4. Once your pond is renovated or cleaned, empty half of the water (not back into the pond)
  5. Slowly fill the rest of the tub back up with the new pond water
  6. After anywhere from a few hours to a day, catch your fish and release them into your new pond

Put Your Fish & Fish Pond In Trusted Hands With Premier Ponds

If you’re looking for a company that can help you with your koi pond maintenance, be sure to reach out to us. We have years of experience keeping these fish safe and healthy, and we’d love to put our expertise to work for you.

Fill out our contact form today and let us know how we can help.