How to run in a New Pond

When planning a new pond, we are careful to create a water feature that blends in well with our garden, in its size, shape and design. Our pond must also be designed with our fish and plants in mind, making sure that the finished project is not only pleasing on the eye, but also pleasing to our fish.

Having designed and installed an appropriately sized pond, the next step in creating a satisfactory environment for our fish is to run-in the pond so it matures, creating a stable and healthy pond into which our fish can be safely introduced.

The running-in process can be broken down into a series of clearly defined steps, each building on the last. Every pond must experience a period of maturation, whether it is a 100 gallon or a 10,000 gallon pond. There are no short cuts in the running-in process as we are dealing with a host of living organisms, ranging from the beneficial bacteria, algae, plants and the fish themselves, all of which obey the laws of nature. However, having said that, it is far easier to run-in and maintain a larger pond as the sheer volume of water provides you (and your fish) with a greater margin for error. For this reason, if you are undecided between two ponds, always choose a larger one.

Step 1. Filling the pond with water.

The vast majority of us use tap water to fill our new ponds. Despite its ‘bad press’, tap water offers us many benefits in that it meets strict quality criteria and is disease-free. However, raw tap water is hazardous to pond life, containing disinfectant additives such as chlorine and chloramine and other pollutants that, over time, can accumulate and cause water quality problems. Tap water can be made fish-safe by adding a tap water conditioner or by passing it through a water purifier on its way to the pond. This is a great opportunity to measure the pond’s volume so that should you ever have to treat it, you can do so with accuracy.

Once your pond is full of water, it is useful to know the pH of your water before anything else is added. This will tell you its suitability for your fish and whether you need to do anything to it before introducing fish. If your water is between 7.5 and 8.5 you are safe to proceed.

Step 2. Add plants

It is safe to add plants as soon as the pond has been filled. Besides looking great, plants will help to condition your pond water, making it less harsh and sterile for other pond life. They will also help reduce algae problems in your pond by competing for light and nutrients dissolved in the new pond water. Choose a selection of deepwater and marginal plants as these will provide your pond with beneficial cover for the fish that you will be adding shortly. Deepwater plants such as lilies or water hawthorn will soon fill the deeper water with cover, racing to the pond surface. Choose taller marginal plants for the shelves at the back of the pond, with lower marginals such as marsh marigold, water mint and lobelia taking front stage.

Step 3. Install pump, filter and UVc.

This trio of hardware is the pond’s life support system and must be installed to suit the size of the pond. The pond water should be recirculated at least every 2 hours, through a filter and UVc that are rated to your pond’s volume. The pump then feeds the filter and UVc with a continuous supply of dirty water that is then processed and returned back to the pond. An external filter is more effective and easier to maintain than an internal pond filter, consisting of a chamber (or series of chambers) filled with a range of media such as bio-foam, porous ceramic media or plastic rings. A brand new filter acts purely as a mechanical device, acting like a sieve, straining out particulate matter. Its vital life-sustaining role (or biological function) is separate from the mechanical side of filtration, utilising bacteria that naturally colonise hard surfaces within the filter. It is the performance and colonisation of these bacteria that determines your pond’s ability to hold fish. As these bacteria are nature’s way of breaking down toxic ammonia that fish excrete, we can only run-in a pond at the same rate as nature allows. We can give a brand-new filter a kick-start by adding bacterial cultures (such as bacterial filter start) or by adding some mature filter media from a friend’s pond.

There are several different types of bacteria that colonise a pond and filter over time, each one exploiting its own niche, breaking down a toxic product (such as ammonia), ultimately making the pond water safe for fish. They require a steady supply of food, oxygen and water, growing faster in warmer water.

The UVc is installed in-line between the pump and filter, and comprises a concealed Ultra-Violet light, over which pond water is passed, preventing green water from colonising your pond. Just as a pump and filter are installed at a size suitable for the pond, so too is a UVc

Step 4. Add the first fish.

The first 2-3 months of a pond’s life are the most hazardous for fish as you try to keep the rate at which fish waste is produced in balance with the rate at which it is broken down by your filter. Any accumulation of ammonia in a pond will soon lead to your fish experiencing fish health problems. If you proceed with caution during this period, finishing with a mature filter system, your fish will benefit and thrive in a stable pond environment. However, if you rush into stocking your pond quicker than your filter is able to cope, you will definitely experience water quality problems that will manifest themselves in unhealthy fish. To be realistic, you should set yourself a 3 month timetable over which you plan to stock your pond with fish. If you proceed any faster, you are likely to encounter problems.

The first few fish will excrete ammonia immediately, providing your filter bacteria with the food they need in order to survive and multiply. Choose some small, hardy goldfish as your first introductions. Only continue to add fish 2-3 at a time if your ammonia and nitrite levels in the water continue to be zero, demonstrating that the filter bacteria are managing to keep on top of the ammonia that your fish are producing.

Step 5. Continue to stock carefully, feed sparingly and test your pond water.

Over the next 3 months, continue to test your pond water to confirm that you are not over stocking or over feeding. If you ever detect a positive ammonia or nitrite reading, stop feeding, carry out a partial water change (to dilute the pollutant) and only resume feeding when pollutant levels have returned to zero. This will allow your filter bacteria to catch up. Repeat this process if ammonia or nitrite levels rise again.

Running-in a new pond is the most hazardous period in a pond’s life. There are no short-cuts to producing a mature pond, as you must work in tandem with nature to produce a stable pond environment that will sustain your fish in good health for years to come. Whatever your pond’s size, by following these 5 steps, you are more likely to achieve a pond full of healthy, vibrant fish.

Kill blanketweed and string algae.