It is important to understand these biological processes in your pond and how to initiate them and measure results. In this article, we will walk through this process step by step and explain the purpose 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 in your pond. The nitrogen cycle ensures that waste and harmful substances are converted into nutrients for your plants.
This waste can originate from:
- Uneaten fish food
- Fish excrement
- Bird droppings
Decomposing waste from plant debris - Algae
- Leaves or branches that end up in the pond
Waste to Ammonia
In the nitrogen cycle, this waste is converted into ammonia. Ammonia is a harmful substance for your fish and plants. It is therefore important that ammonia is converted into nitrite as quickly as possible.
Ammonia to Nitrite
Over time, bacteria will develop in your pond that convert ammonia into nitrite. Nitrite is also a harmful substance for your fish. You want to keep nitrite levels as low as possible in your pond. Therefore, it is important that nitrite is also converted into the less harmful nitrate.
Nitrite to Nitrate
The last step in the nitrogen cycle is the conversion of nitrite to nitrate. As soon as nitrite is produced in your pond, bacteria will develop that convert it into nitrate. Nitrate is (as long as the levels are not too high) not harmful to your fish and is even an essential nutrient source for the plants in your pond.
2. Starting the Nitrogen Cycle
When you start a new pond, the nitrogen cycle in your pond must be started. A new pond does not yet contain enough of all the necessary bacteria to achieve the balance in the ecosystem that you ultimately want.
After filling your pond with water, the nitrogen cycle will start automatically. The first step in the nitrogen cycle is converting waste into ammonia. Because there is often virtually no waste present in a new pond, you will have to add waste to your pond. You can do this by starting to feed (without having any fish in your pond yet). By gradually building up food, bacteria in the nitrogen cycle get the nutrients and thus the chance to grow.
You can also add some fish to start the cycle in your pond. Too many fish, waste or rotting 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 that there are not too many fish or waste in the pond in the beginning.
Also make sure that when you add fish for the first time, the ammonia and nitrite levels are not too high.
As soon as ammonia is present in the water, the nitrification process will start. The conversion of ammonia into nitrite (which is also harmful to your fish). Subsequently, bacteria will also develop that convert nitrite into nitrate.
The bacteria that convert ammonia into nitrite and the bacteria that convert nitrite into nitrate grow slowly. It can therefore take 4-6 weeks before this process is fully up to par.
The nitrate 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 means too much food for plants again. This can ultimately result in an algae 'boom', an explosion of algae within a few days. This can make your water green and cloudy.
To prevent excessive algae growth, you can ensure that less waste/food enters the water or connect a UV-c device to combat algae.
The activity and functioning of the ecosystem vary depending on the weather and climate throughout the year. Read all about the impact of this on your pond in our article about 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 are ultimately found throughout your pond. Most bacteria will attach to surfaces. Think of stones, plants and in a filter. In a pond, the amount of available surface area for bacteria to grow can be limited. Adding a filter provides extra surface area where bacteria can grow. In addition, a filter ensures that all the water in your pond is passed through your filter. This way, the ammonia and nitrite that are present are guided along the bacteria in your filter.
4. How a Filter Works
It is often thought that a filter for a pond removes small pieces of dirt. Although a filter also does this, this is not the purpose of a filter. The purpose of a filter is to support and strengthen the nitrogen cycle. A filter does this thanks to the different types of filter media and the flow in the filter.
Different Types of Filter Media
The purpose of a filter is to be a breeding pond for the bacteria in the nitrogen cycle. This happens in a filter by growing as much surface area as possible where the bacteria can attach to and grow on. Many different types of filter media are suitable for this. You often use several types of filter media in a filter, so that the bacteria can grow on the different types.
Some well-known examples of these filter media are filter sponge, stones, brushes and plastic filter balls. The filter media must have as much surface area as possible for the bacteria to attach to. At the same time, the water from the pond must still be able to flow past the filter material.
Flow in a Filter
A pond pump ensures that all the pond water is sent through the filter throughout the day. It is possible that parts of the water flow through your filter 2 times or more per day. How often this happens is important for the type of pond you have. You can use the following amounts for this.
- Pond with only water and no plants or fish - at least every 2 hours
- Pond with plants and without fish - at least every 4 hours
- Pond with fish and plants - at least every 3 hours
- Pond with only fish - at least every 1.5 hours
Calculation example
Suppose you have a pond of 9,000 liters. You have fish and plants in your pond. 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 per 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 through your filter as often. Your filter therefore needs less capacity. This is because plants themselves also act as a filter. Plants also purify the water because bacteria attach to the plants and the plants absorb nitrate as nutrients.
5. Choosing a Filter System
There are different types of filters that you can use to filter the water in your pond:
- Gravity filter
In this, water is guided through a filter by gravity. You need a pump to get the water into or out of the filter. Then gravity does the rest. A gravity filter often has 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 that flows into the filter remains under pressure. This way you can easily send the water somewhere again via a hose. This gives you more flexibility 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 contain a pump, filter material and UV-c device. You often place the all-in-one filter underwater and do not have to sacrifice any space around your pond. - Natural filter
Plants can have a filtering effect on your pond. Just like in a filter system, bacteria can attach to the plants. With a natural filter you create a separate basin in your pond where you let water flow past.
Want to know more or need help setting up your pond? Contact the customer service of BluGarda.