Aeration in aquaponics is by far one of the most important factors which can determine the success of the entire system. The air pump keeps the bacteria, fish and the plants alive as they all require air to carry out their daily functions. When dissolved oxygen becomes too low, fish, plants and other aquatic organisms cannot survive.
Choosing an air pump for an aquaponics system depends on factors such as fish stock, plant density, water volume, turbulence and depth of the water in the fish tank. These factors determine the quantity of dissolved oxygen needed and the size of the air pump required to supply oxygen for the system.
The process of respiration occurs continuously in an aquaponics system, and organisms from the fishes to bacteria, all need air to survive. You can simply purchase any air pump from the local pet store but will it provide enough oxygen for the entire system to run efficiently?
Air pumps come in all different types and sizes and getting the right size to properly aerate your system would take a little “know how”. We are going to discuss everything you need to know in this article to properly set up your system for success.
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What does an Air Pump do?
An air pump supplies oxygen to water by pumping air from the atmosphere into the water in the form of bubbles. The air pump works well with air stones which helps to further break up the bubbles into smaller ones for maximum oxygen to be dissolved into the water.
Fishes and plants use this vital oxygen to carry out their daily functions.
What Determines the Size of the Air Pump my Aquaponic System Needs?
An aquaponics system is a closed loop circulating eco system in which bacteria, plants and fishes all thrive in symbiosis. These are biological organisms that require oxygen for energy production by oxidizing complex organic substances.
An air pump is used to inject air into the water which creates bubbles.
How does the oxygen actually get into the water?
In fact, air pumps don’t directly add oxygen to the water, but by creating turbulence, the oxygen gets dissolved into the water.
Turbulence of the Water –
Turbulence is also created by the circulation of water throughout the system. As water is circulated it passes through the different components.
It starts from the water pump which lifts it into a fish tank then to the mechanical and bioflter respectively, then through the plants and grow beds and eventually ends back up in the sump where the cycle starts all over again.
Turbulence is therefore something to take into consideration when getting an air pump for the system.
Turbulence is the way oxygen gets dissolved into the water.
The Amount of Fishes in the System (Fish Density) –
The fishes uses up the majority of the dissolved oxygen in an aquaponics system. Depending on the amount of fishes there are living in the tank, you can have a better idea of the aeration requirements.
The total biomass of the fishes increase as time passes this is because as they eat food they grow bigger and would therefore, require more air.
Tilapia fishes require 4.5 grams of oxygen per 100 pounds of fish per hour.
ie. An average 6 month old Tilapia weighing 2 pounds would require 0.09 grams of oxygen in an hour.
Yea, Some crazy mathematics but you can simply ensure with a properly sized air pump there is enough turbulence required for proper aeration.
What you don’t want is when your system is running you see the fishes swimming to the top of the water. Whenever you see this happening you know there definitely is not enough dissolved oxygen in the water for the fishes.
And if the oxygen is not enough for the fishes then you know the rest of the system is also starving for oxygen as well and immediate intervention is required.
The Size of the Fish Tanks –
From the size of the fish tank in your system, you would have an idea of how much water there is circulating in the system. Water is the medium by which oxygen is carried throughout the system to the different users.
The rate at which oxygen dissolves in water is affected by the temperature of the water.
The warmer the water the less oxygen gets dissolved.
Let say your the fishes in your aquaponic system are kept in an IBC tank.
A IBC tank would contain an average of 250 US gallons of water. With the water contained in the mechanical filter (~55gallons), the Biofilter(~55gallons) and the sump(~20 gallons). That is approximately 380 gallons of water circulating in this system.
With a circulating system like this, the dissolved oxygen would be able to support about 10 full grown tilapia fishes and the demand of the rest of the system, plants and bacteria included.
The rate at which oxygen is dissolved into the water should be sufficient to ensure the fishes, bacteria and the plants have sufficient amounts of oxygen to live healthy.
The Amount of Plants in the Grow beds –
Plants too require oxygen to survive since they themselves respire. Plants undergo aerobic respiration which uses oxygen and produces carbon dioxide. Photosynthesis however uses carbon dioxide and produces oxygen.
The more plants in the system the more oxygen they would require. As plants grow over time, just like the fishes the oxygen demand will also increase and this should also be taken into consideration
The Depth of the Water in the Fish Tank –
The depth of the water also plays a part in choosing the size of air pump you may need. The deeper the placement of air stones the more force would be required to push air our of the stone and into the water.
In some cases it is not necessary to place the air stones at the bottom at the tank. I however, recommend placing the air stone at the bottom of the tank because apart from more aeration the air bubbles also churns up the water and prevents heavier fish waste from settling at the bottom of the tank.
How can I Aerate Fish Water Without an Air Pump?
The water in an aquaponic system can stay oxygenated without an air pump if there is enough turbulence in the system to provide oxygen absorption.
The amount of fishes in this case would therefore have to be significantly less than if there was an air pump attached to the system. Fishes can eat up a great deal of dissolved oxygen depending on their size and stress levels, so keeping the fishes happy is a must. Even if it means getting an additional air pump.
Designing a system such that it runs on a single pump, the water should only have to be lifted once and this is done by the water pump. The rest of the system should be designed such that the water flows sequentially through all the components by gravity flow. You can now use gravity to allow the water to have a cascading effect into each component.
The cascading effect is similar to that of a waterfall and creates maximum turbulence as the water circulates through the system.
This type of system is known as a
CHOP system (Constant Height One Pump)
Another way the water can be aerated without an air pump is by use of a venturi. A venturi is a restriction in the piping which speeds up the flow of water at the restriction causing a negative pressure at that point.
This negative pressure is utilized by placing a hose which is open to the atmosphere. Air is then sucked in into the hose causing air bubbles to go along with the stream of water and in turn aerating the water.
Want to learn how to make a venturi for Aquaponics? I have written an entire article on how you can easily do it using simple materials.
What can cause the Dissolved Oxygen in the Water to Drop?
The dissolved oxygen in an aquaponic system can fall because of a number of reasons.
- Algae starts to invade the Aquaponics system
- The air pump stops for some reason
- The air stones gets fouled.
- The temperature of the water increases
- As the biomass of the fishes increases
- There is additional plants in the system
- There is other organisms in the system eg. snails
If left unchecked algae can wreak havoc on any aquaponics system. Algae are non-flowering simple aquatic plants and are usually bright green in color. They can multiply rapidly and deplete the dissolved oxygen and nutrient supplies in the system.
The depleted resources can lead to the death of both plants and fishes. Sunlight can have a direct impact on the rate at which algae grows and they are normally found in the fish tank which is the most opened to the elements.
The Air Pump Stops –
If the air pump stops the quantity of dissolved oxygen will drop rapidly and fast since the primary source of aeration has been stopped. What you can do in this case, is connect a venturi at the end of the pump or at the pump’s direct outlet.
Most pumps that are made for aquaponic systems come with this feature and it is as simple as connecting a tubing to a special fitting which comes with the pump. So look for this when purchasing a pump for your system.
I have written an entire article on choosing the most efficient pump for an Aquaponic system. Have a read!
The Air Stones gets fouled –
The purpose of the air stones is to break up the supplied air from the air pump into smaller bubbles. The smaller bubbles increase the surface area of the which allows more oxygen to be dissolved into the water.
Over time as the system ages the air stones tend to get fouled with moss and other materials. This fouling can lead to the pores in the air stone to become plugged reducing it’s ability to break up the air into smaller bubbles and as a result less oxygen gets dissolved into the water.
Regular system maintenance helps prevent such occurrence and ensures that there is always a steady supply of bubbles into the water.
The Temperature of the Water Increases –
The ability of oxygen to dissolve into water is directly affected by the temperature of the water. The hotter the water, the harder it would be for oxygen to dissolve.
For this reason may aquaponic farmers resort to covering the fish tanks and the entire system to prevent the water temperature from going too high. This is very typical for farmers living in tropical regions or in states where the temperature can get well over 100oF.
Increase in Biomass –
The biomass of the fishes is simply the total mass of all the fishes in the system. The biomass will increase if more fishes are added to the system or as the fishes grow naturally.
With additional biomass, the oxygen requirements of the fishes would increase. Hence, more aeration would be required to maintain the health of the fishes.
Additional Plants in the System –
Plants too need oxygen. As they grow, or if more plants are added into the system, more air will also be required.
So thinking about adding that extra floating raft of plants? You would not only have to consider the nutrient requirements but also the oxygen requirements of the plants. Then you may have to increase the aeration in the system.
Other Organisms in the Aquaponic system –
Aquaponic system can also be plagued by invasive species. On such species is aquatic snails.
Short story! I caught a few wild tilapia once from a nearby pond. I was happy to add it into my system because you know, it’s free! So I added the fish. There were about 10 in total.
After a few days I noticed these black spots all over the fish tank and the plant rails. On a closer look I plucked one out and the black spots were aquatic snails. They were like ants, all over the system and were also sucking up the oxygen in the system
I had to destroy the plants and give the entire system a thorough cleaning. For this reason, I strongly suggest not to use wild fishes in your aquaponic system unless they are sterilized in a holding tank separately for a couple days to see if they are carrying any baggage.
Can Fish Sleep with the Air Pump On?
Fishes can sleep with the air pump. The fishes tend to get accustomed with the constant humming and popping bubbles that come from the air pump.
However, they will notice when the pump goes out after some time and their inquisitive nature will kick in. But this may not be a good thing. Additional stress placed on the fishes cause them to use more oxygen. It’s the same as running, we breathe more frequent and deeper breaths.
An air pump with an air stone should not have any effect on the daily cycle of the fishes.
Will fish Die without Air Pump?
The fishes may or may not die without an air pump. Depending on how the system is designed, referring to the CHOP system. Gravity flow would help with aeration as the water cascades into the different components.
However, if the aquaponics system is loaded with fishes and plants for the amount of air that is being supplied, they would eventually die.
In this case you should look into getting a backup air pump in the event that this one fails or if there is a power outage.
Do you Need an Air Pump for Aquaponics?
In most cases you would need an air pump for your aquaponics system. If your system is small and your fish stock is small you can incorporate the use of a venturi and water turbulence to introduce dissolved oxygen into the water without the use of an air pump.