Complete guide to how the ecosystem and filtration of your pond works

Your pond is a mini ecosystem in which many biological processes take place. These biological processes are essential for a healthy pond. But if you set up your pond incorrectly or are in too much of a hurry to set up, the biological processes can be deadly to the fish in your pond. With proper setup of these processes, your fish will stay healthy and the plants in your pond will grow well.

It is important to understand these biological processes in your pond and how to get them going and measure results. In this article, we will go through this process step by step and explain the usefulness and necessity of a filter for your pond.

1. The nitrogen cycle

The most important biological process in your pond is the nitrogen cycle. This cycle occurs everywhere in nature, including your pond. The nitrogen cycle converts waste and pollutants into nutrients for your plants.

This waste can come from:

• Leftover fish food that has not been eaten
• Fish excrement
• Bird droppings
  Rotting plant waste
• Algae
• Leaves or branches that end up in the pond

Schematic drawing of the nitrogen cycle in the pond

Waste to ammonia

This waste is converted to ammonia in the nitrogen cycle. Ammonia is a harmful substance for your fish and plants. It is therefore important that ammonia is converted to nitrite as quickly as possible.

Ammonia to nitrite

Over time, bacteria develop in your pond that convert ammonia to nitrite. Nitrite is also a harmful substance for your fish. Therefore, you want to keep nitrite levels as low as possible in your pond. Therefore, it is important that nitrite is also converted back, to the less harmful nitrate.

Nitrite to nitrate

The last step in the nitrogen cycle is the conversion of nitrite to nitrate. Once nitrite forms in your pond, bacteria will arise and convert it to nitrate. Nitrate (as long as the levels are not too high) is not harmful to your fish and even an essential food source for the plants in your pond.

Nitrogen cycle on Wikipedia

2. Starting the nitrogen cycle.

When you start a new pond, the nitrogen cycle in your pond has yet to be started. A new pond does not yet contain enough of all the necessary bacteria to get the balance in the ecosystem you eventually want.

After filling your pond with water, the nitrogen cycle will start on its own. The first step in the nitrogen cycle is to convert waste into ammonia. Because there is often virtually no waste in a new pond, you will need to add waste materials to your pond. You can do this by starting feeding ahead of time (without already having fish in your pond). By building up feed slowly, bacteria in the nitrogen cycle get the nutrition and thus the chance to grow.

You can also add a few fish already to get the cycle going in your pond. Too many fish, trash or decaying material in the pond can cause an ammonia or nitrite spike in the start-up phase. These can be harmful to the fish already present. So make sure there are not too many fish or trash in the pond in the beginning.

Also make sure that when you first start adding fish, the ammonia and nitrite levels are not too high.

Once ammonia is present in the water, the nitrification process will start. Converting ammonia into nitrite (which is also harmful to your fish). Next, bacteria will also arise that convert nitrite into nitrate.

The bacteria that convert ammonia to nitrite and the bacteria that convert nitrite to nitrate grow slowly. As a result, it may take 4-6 weeks for this process to reach full maturity.

The nitrate eventually produced is absorbed by plants, among other things. Nitrate is not harmful to your fish, as long as there are no extreme levels of nitrate in your pond.

Too much nitrate in turn means too much nutrition for plants. This can eventually result in an algae "boom," an explosion of algae within days. This can turn your water green and cloudy.

To prevent too much algae growth, you can make sure there is less waste/food in the water or connect a UV-c device to control algae.

Ecosystem activity and function vary due to weather and climate throughout the year. Read all about how this impacts your pond in our article on maintenance and preparation for your pond for all seasons.

3. The importance of a filter for the nitrogen cycle.

The bacteria needed for the nitrogen cycle will eventually be found throughout your pond. Most bacteria will attach to surfaces. Think rocks, plants and in a filter. In a pond, the amount of surface area available for bacteria to grow may be limited. Adding a filter provides additional surface area for bacteria to grow. In addition, a filter ensures that all the water in your pond is carried past your filter. Thus, the ammonia and nitrite present are routed past the bacteria in your filter.

4. How a filter works

It is often thought that a filter for a pond takes out small pieces of dirt. While a filter does this as well, this is not the purpose of a filter. The purpose of a filter is to support and enhance the nitrogen cycle. A filter does this thanks to the different types of filter media and flow in the filter.

Different types of filter media

The purpose of a filter is to be a breeding ground for the bacteria in the nitrogen cycle. This is done in a filter by cultivating as much surface area as possible for the bacteria to attach to and grow on. Many different types of filter media are suitable for this purpose. You often use multiple types of filter media in a filter as well, so that the bacteria can breed on the different types.

Some well-known examples of these filter media are filter sponge, stones, brushes and plastic filter balls. The filter media should have as much surface area as possible for the bacteria to adhere to. At the same time, the water from the pond must still be able to flow past the filter media.

Flow-through in a filter

A pond pump ensures that all pond water throughout the day, is sent through the filter. It may be that portions of water flow through your filter 2x or more often per day. How often this happens is important for the type of pond you have. You can use the following quantities for this.

• Pondwith only water and no plants or fish - at least every 2 hours
• Pondwith plants and no fish - at least every 4 hours
• Pondwith fish and plants - at least every 3 hours
• Pond with fishonly - at least every 1.5 hours

Calculation example
Suppose you have a 9,000-liter pond. In your pond you have fish as well as plants. This means that the water in your pond must flow through your filter every 3 hours. This means that at least 3,000 liters of water (9,000 divided by 3) must pass through your filter every hour.

Furthermore, you can see that plants have a positive effect on your filter system. Plants ensure that the water in your pond does not have to pass your filter as often. So your filter needs less capacity. This is because plants themselves also act as a filter. Plants also purify the water because bacteria attach themselves to the plants and the plants absorb nitrate as nutrients.

5. Choosing a filter system

There are different types of filters you can use for filtering the water in your pond:

• Gravity filter
  In this, water is passed through a filter by gravity. You need a pump to get the water in or just out of the filter. Then gravity does the rest. A gravity filter often contains several chambers, each containing its own type of filter material.
• Pressure filter
  Suitable for small to medium-sized ponds. In a pressure filter, the water flowing into the filter remains under pressure. Thus, you can also easily send the water back somewhere via a hose. You are thus more flexible in placing the filter around your pond.
• All-in-one filter
  With an all-in-one filter you get everything you need to filter the water in your pond with one device. These often include a pump, filter material and UV-c device. You often place the all-in-one filter underwater and do not have to sacrifice space around your pond.
• Nature filter
  Plants can have a filtering effect on your pond. As in a filter system, bacteria can attach themselves around the plants. With a nature filter, you create a separate basin in your pond that you allow water to flow past.

Want to know more or need help setting up your pond? Contact BluGarda's customer service team.