Part 1 is all about the Bio-Chemical Process behind an AP System.
You need to understand the Bio-Chemical Process to understand what makes an AP System work.
You're going to learn some brand new scientific terms; but just take your time and read this Part carefully. A lot of what happens Bio-Chemically is automatic. All you need to do is know it's happening. OLIVER
Aquaponics 101 Part 1: The Bio-Chemical Process, an Introduction of the Nitrogen Cycle
What is Aquaponics and why should I care?
Aquaponics is an ancient food growing technology that has been around since the Earth has had water with fish and plants growing together naturally. Aquaponics is nature at work. In nature, the fish eat whatever they find for food, and their waste is broken down by the bacteria in the water creating nutrients for the plants. The plants that receive that nutrient rich water then absorb these nutrients; and in doing so, they help clean the water for the fish.
The word "Aquaponics" comes from two separate words. The first word is "aqua", which, of course, means water; but in this case, the "aqua" is from another compound word "aquaculture" (the raising of fish). The second word is "ponics", which is latin for work, and comes from its use in "hydroponics" (working at growing plants in water, hydro).
So, Aquaponics is raising fish and growing plants by using the nutrient rich water provided by the fish.
The reason one should care about Aquaponics is that it is a year-round food growing technology, which can supply you and your family with fresh veggies and fish regardless of the season. Most fish species take a year or more to grow out to edible size. Because of this long term growth, the system must be placed in an environment that allows for year-round operation. In tropical climates, an Aquaponics system can work outside with minimum cover. In milder climates, it must be placed in an environmentally controlled green house. In harsh climates, it must be placed indoors with grow lights to replace the sun and grow your plants.
The plants grown in an AP system grow out in less time, grow year round, can be planted more densely, are tastier and require 90% less water than does tillage farming. Also, if the AP system is properly designed, it takes up much less space than does tillage farming. Some plants can be grown directly in the fish tank to absorb the nitrates from the water as any one who owns an aquarium knows. Most AP farmers separate their fish tanks from their plant grow beds allowing them more flexibility in the way they grow and in what they grow. The water is circulated between the fish tank and the grow bed using a pump. This is known as a recirculating aquaculture system that contains two food sources, fish and vegetables. Some grow their fish for food while others keep their fish as pets that also serve a useful purpose, which is fertilizing the plants.
But there is a third living organism in the AP equation, the beneficial bacteria. They are the pro-biotic of the system and live in what is called a bio-filter. Just like the name says, the pro-biotic (beneficial bacteria) filters the waste in the water, not by removing it, but by converting it into nitrates. Where this takes place could be called a bio-converter, but it is generally called a bio-filter instead.
In an aquarium, where there are only a few fish for the amount of water, the bacteria live in the water, the sand on the aquarium bottom and on any surface where they can attach themselves. In an aquaponics system, the amount of fish per gallon of water is much higher than what is usually found in an aquarium. This higher fish density requires an additional amount of filtration; therefore, a bio-filter becomes an important part of the recirculating water path in the system.
Before discussing bio-filtration, I want to address the concern some may have for the high density of fish in the system. In a home or school AP system, we are talking about one pound of fish for about every six gallons of water maximum at full fish growth. Commercial fish farmers usually run much higher densities, which requires special filtration and oxygenation of the water. Even at six gallons per pound of fish in the system, the fish tend to school together somewhat because it's the nature of fish to create schools. They were introduced into the same tank when the were very small, grew up together and like to hang out with each other. When fish get stressed, you will know it by their unnatural behavior. At these densities, your fish will appear relaxed and healthy. I will be discussing the fish in much more detail in a later segment.
There were 5 Deep Media Grow Beds in our original Greenhouse System Design. Since these photos were taken, we have re-desined our Greenhouse.
The Nitrogen Cycle:
The fish give off two types of waste, which, and if allowed to accumulate, is toxic to them. As with any living organism, fish cannot live in their own accumulated waste. The first type of waste is ammonia, which is secreted from the gills and found in the fish urine. The second type is fish waste solids. We refer to this as fish effluent or commonly called poo.
The required bio-filter is a part of the AP system. In many systems, media filled grow beds double as the bio-filter because the media has a large amount of surface (substrate) area and the grow beds function not only as beds within which to grow the plants but also as a place where most of the bacteria in the system live that feed on the ammonia. These bacteria, known as autotrophic bacteria, attach themselves to any surface they find. Their job is to convert the ammonia into nitrates.
This is a two step process. First, one type of autotrophic bacteria converts the ammonia to nitrites by splitting the ammonia into nitrogen and hydrogen. The nitrogen (N) is then combined with oxygen (O2) found in the water in the form of dissolved oxygen and in this process forms nitrite (NO2). For the chemists reading this, it is NH3 or NH4 + O2 -> NO2 + H2. Both the nitrite and the hydrogen are released back into the water.
The nitrites (NO2) produced are also toxic to fish in relatively small quantities, just like the ammonia. So, the second bacteria comes into play to add some more oxygen to the nitrites converting them into nitrate (NO3). Note the spelling, nitrite (NO2), nitrate (NO3). Now, nitrates (NO3) are not very toxic to fish and generally, depending on the species of fish, they can tolerate 100 times more nitrates in the fish water than they can ammonia or nitrites.
Here's where an AP system becomes symbiotic (mutually beneficial). Plants need and love (absorb) nitrates, so the nitrates won't stay or accumulate in the water to high levels unless there are fewer plants than needed to absorb (uptake) all the nitrates generated by the fish and bacteria processes I just described.
This brings us to the solid fish waste. The good news is that nature provides. In this case nature provides us with another type of bacteria known as heterotrophic bacteria. Heterotrophic bacteria live in the water and attach themselves to any dead organic matter like uneaten fish food, dead plant roots or solid fish waste. Through a process called mineralization, the heterotrophic bacteria convert these leftovers into their component parts, which then become nutrients for the plants. Heterotrophic bacteria also produce their own waste, which is more ammonia; and it is converted by the autotrophic bacteria mentioned above into nitrates for the plants. In addition, heterotrophic bacteria help keep the water in the fish tank clean and clear. Heterotrophic bacteria also require and consume the dissolved oxygen (DO) in the water in order to live and do their work. So, heterotrophic bacteria take organic suspended solids in the water and convert them to dissolved solids that can be utilized by the plants while they consume dissolved oxygen.
It is important to note that the above processes each require and use DO found in the water (as do the fish and plants) and deplete it from the water as they go about their business. This DO must be replaced on a continuous basis or the process will not work properly. I will discuss the importance of ample DO in your system in a later part.
The plants, which are planted in the grow beds, receive the nutrient rich water containing all these wonderful ingredients including DO, uptake them along with some water and use them to grow. The remaining water now has reduced amounts of nutrients, and it is returned to the fish tank for use by the fish. So, the fish are fed by the AP farmer, and their waste feeds the bacteria. The bacteria convert their food (fish waste) into bacteria waste that feeds the plants. The plants uptake the nutrient rich food provided by the bacteria. The water is cleaned in the process and returned to the fish. These symbiotic relationships are on-going as this is a recirculating aquaculture system that has both fish and plants as well as natures gift of beneficial bacteria working away, and it is known as Aquaponics.
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Congratulations! You've just completed Aquaponics 101 Part 1.
Now it's time to test your knowledge. Take the Part 1 Quiz below:
1. What is Aquaponics?
2. How long does it take most edible fish species to Grow Out?
3. In what climate can you set up an AP System with minimal
4. What is the Growing Season for Aquaponics fruits and veggies
when the AP System is in a controlled Greenhouse?
5. How much less water is used in Aquaponics farming compared
to tillage farming?
6. Besides fish and plants, what is the general name of the third
living organism in an AP System?
7. What are the names of the two types of this third living
8. Where do each of the two types of this third living organism
live in system?
9. How many kinds of waste do fish give out?
10. What are the names of these kinds of waste?
11. Besides holding your plants, what second important role do
Media-filled Grow Beds play in an AP System?
12. What is the name of the bacteria that converts ammonia into
13. The fish can tolerate _____ times more Nitrates than Nitrites
14. Besides fish food, what needs to be replaced on a continuous
basis for the system to work properly?