What is an aquaponics biofilter?

An aquaponic biofilter provides the ideal environment for beneficial bacteria to thrive in aquaponics. The biomedia offers a vast surface area for bacteria to dwell in an aquaponic system and transforms fish waste into plant nutrients.

This biofilter is generally put right after the mechanical filter and plays a vital role in the designing, architecture, and operation of a successful aquaponic system.

The biofilter and mechanical filter work side-by-side because the mechanical filter eliminates the heavier fish waste first, while the biofilter does not become overloaded and blocked.

A biofilter is a container, such as a canister, tank, or barrel that carries a well-aerated porous medium. The water from the fish tank passes through the biofilter, where ammonia is transformed to nitrite and finally to nitrate.

What is biofiltration?

Biofiltration is the process by which helpful microorganisms convert ammonia and nitrite to nitrates. Even at low concentrations, ammonia and nitrites are hazardous to aquaponics. Plants, on the other hand, require nitrates to develop. Thus a biofilter must be placed to contain the majority of active bacteria. The tiny biowaste matter not sieved by the mechanical filter will be broken down by the water movement within a biofilter, preventing waste buildup on the plant roots in the aquaponics system. The chemical stability of your aquaponics system is also dependent on good biofiltration.

What is the relationship between nitrification and water pH range?

When it comes to temperature and pH, there is a bit of a compromise in aquaponics. Such a fact applies to the needs of the fish and plants. A grower should aim to suit the bacteria's environmental requirements to keep any aquaponics arrangement healthy. To achieve this, the pH level of the water in the biofilter should be 7.0 or a little more beyond that. The reason behind this is in such a range, nitrification is at its peak.

The benefits of using calcium hydroxide instead of potassium hydroxide to increase pH levels are threefold, according to researchers from the University of Virginia Islands. One is that the pH is adjusted to keep it neutral, and the other is that calcium and potassium, which are occasionally in short supply for plant growth, are supplemented as a result. The nitrification rate reduces when the pH dips below the required range, and nitrification nearly stops as the pH drops further.

What is the relationship between nitrification and bacteria in aquaponics?

In an aquaponics system, nitrifying bacteria play a crucial function. Fish waste, which enters the system as ammonia, is converted by nitrifying bacteria into nitrates, which fertilize the plants. In aquaponics, nitrification is a two-step process involving two nitrifying microbes:

  1. Ammonia to nitrites: Ammonia is converted to nitrites by Nitrosomonas bacteria. When food waste is abundant, the Nitrosomonas creates excess ammonia in the water. To keep the fish healthy, ammonia must be removed.
  2. Nitrites to nitrates: Here, the bacteria Nitrobacter and Nitrospira are operating. These bacteria feed on nitrites producing nitrates in the process. Plants grow well when they receive nitrates.

How does an aquaponics biofilter work?

The biofilter works by containing microorganisms that convert ammonia from fish waste into nitrates needed for plant growth. The biofilter's environment should be bacteria-friendly. Nitrification is a two-step process that accomplishes this.

The biofilter extends your aquaponics system's surface area. It's an essential component of your aquaponics system since it ensures that your plants have access to the nitrates they require while also cleaning the water for the fish. The bacteria will adhere to the biofilter media's surface. They conduct their function and convert ammonia and nitrites to nitrates once they've established themselves.

In aquaponics, there are three primary processes to biofiltration. This is how you put up a conventional aquaponics system. Depending on the architecture of your biofilter, the process or steps may differ.

  1. The water from the fish tank is pumped into the biofilter by the air pump.
  2. The water passes through the nitrification process inside the biofilter. Good bacteria aid in the conversion of ammonia and nitrites to nitrates.
  3. The nutrient-rich water exits the biofilter and runs into the plants, where the roots absorb the nutrients while cleaning the water before returning it to the fish tank.

Why use an aquaponics biofilter?

You are undoubtedly aware that a decent aquaponics system would not require much from the grower. It is typically enough to feed the fish and keep an eye on the water quality, particularly pH, ammonia, and nitrates. And now you beg the question, "Why should I use a biofilter in my aquaponics system?"

The biofilter is designed to convert ammonia (fish waste) into nitrites and eventually nitrates, which plants can eat. You'll need nitrifying bacteria in your aquaponics system's grow media to accomplish this.

However, if your growing media lacks an adequate surface area, there will not be enough bacteria to complete their function in your system. To put it another way, bacteria are in charge of turning ammonia into nitrates for your plants. If your grow media's surface area is insufficient and you don't have the space to add more, you'll need a biofilter.

Simply put, a biofilter is a space for bacteria to proliferate. Large surface areas, correct temperature, pH, and dissolved oxygen levels are all provided.

Another reason some growers will install a separate biofilter to an aquaponic system is to ensure that biofiltration continues even if they are not using the plant grow bed but are still running the fish tanks.

What are the different types of biofilters?

Three types of biofilters are used today by aquaponics practitioners. These are the moving bed filter, static filter, and drip filter.

Moving bed filters

This biofilter is employed in a floating raft system where the bacteria have limited surface area. The K1 media kit is commonly used for moving bed biofilters. A K1 media kit is made up of small, circular pieces that offer the bacteria the most surface area possible to collect on. It stays with the raft and floats along the water like plant rafts, cleaning the water in the process.

In a nutshell, a moving bed filter is a nitrate factory. It uses tiny filter material with a large surface area to capture all bacteria that pass through the filter. The concept is comparable to how aquaponics works. The same naturally occurring bacteria, Nitrosomonas and Nirospira, are cultivated in the filter media. These filters act as a small nitrogen cycle, filtering the water. The filter media is named from the fact that it works best while it is moving around in the water.

Static filters

This type of filter is opposite to the first one. The filtering media is only "static" or "stationary." In fact, static filters are flat-tray filters that can be slotted into a separate container next to your tank, before the plants, and give a considerable surface area for bacteria to settle on. You can choose the density that best meets your needs; the denser the media mat, the larger the surface area, and the more nitrifying bacteria there are.

They will need to be installed after the solids filter, before the water is pumped to the plants, to allow the water to be filtered before it reaches the plants.

Drip filters

A filter that enables water to drip through from the top is the third choice. It travels through a filter box containing lava rocks, oyster shells, or another biomedia with a large surface area. This setup is ideally placed after the water has exited the fish tank, preferably after your solids filter and before it reaches the plants. Ammonia will be converted to nitrates when the water passes through this filter, allowing it to be piped into the plant growing component of your system.

What are the factors to consider in using biofilters for aquaponics?

Before venturing in using biofilter for any aquaponic setup you have in mind, it is recommended that you consider the following factors:

Solid wastes

The biofilter for aquaponics is designed to deal with tiny fish effluents. Large chunks of solid wastes could block the pipes leading away from the biofilter tank or container. Consequently, your biofiltration will become overwhelmed. One effective means of solving this issue is installing a mechanical filter that will strain the large pieces of fish waste.

Aeration of the microbes

The bacteria in a standard aquaponics system will be exposed to air. This situation could be due to the flood and drain method, which introduces air every time it drains. It could also be because a portion of the growth media is constantly exposed to the air.

The addition of an aquaponics biofilter makes it self-contained, but it may deprive it of the oxygen that bacteria require to thrive. To ensure that the biofilter can perform its function optimally, you must ensure its adequate air supply.

Stocking density

Biofilters are necessary for growers who breed large quantities of fish since the wastes they produce could overburden the system. If your fish stocking density is low, then biofilters would not be a requirement. The exposed plant roots will provide sufficient surface area for the ammonia to be converted to nitrates.

What design should a biofilter have?

For your biofilter to be successful in performing its intended function, observe the following design below:

  1. Waterflow direction A biofilter should be constructed so that water enters at one end and exits at the other. This design guarantees that the water inside the biofilter will reside at the longest available time. More ammonia to nitrate conversion would occur once the water spent more time within the filtration tank.
  2. Adequate air supply - If you are using air stone, it should be placed beneath the biofilter tank for the air bubbles to move upward. By doing so, the entire container is sufficiently oxygenated.
  3. Surface area and microbes ratio - More bacteria equals more surface area. For the biofilter to function correctly, it must increase the surface area by employing the appropriate biomedia.

One of the strengths of aquaponics is to imitate what is happening in nature. An effective way to attain this is by introducing a biofilter to the aquaponics system. Even though this only applies to large fish stocking density, a biofilter is a sure way of helping your plants receive the nutrient they need to grow optimally.

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