Aquaponics is a highly adaptable system for food production that can easily be done at home. It closely resembles the natural relationships found in the wild between fish, water, and the surrounding plants in that the fish waste is fed to the plants and the plants keep the water clean for the fish. This system requires very few inputs and has none of the harsh outputs found in hydroponics or aquaculture. It really is the best of both worlds! A well built well kept system can produce a lot of food in a small area (food density).
This article is going to teach you the basic concepts of aquaponics and show you where you might continue your research. It is very hard to show teach you everthing about this topic because each aquaponics system needs to be adapted to the location you live in. Hopefully this information will help you understand why we use aquaponics on our farm and why we think it really is the way going forward for our society to produce food for itself in a self sustaining manner.
The simplified version of how it works
Live fish are raised in a tank of water. The water in this container, which contains normal fish by-product (waste), is pumped out of the tank and into grow-beds. Grow-beds (generally around 12" deep) are containers filled with some sort of grow media (gravel, clay pebbles, etc.) and plants planted at the top of the bed. The media in the grow-beds will eventually become the home of beneficial bacteria that will eventually convert the fish waste into food for the plant. The plants can then consume the food. The water is returned from the grow-bed back to the fish tank generally via gravity. You now have healthy fruits, vegetables, and fish to consume. The fish stay healthy because they are constantly surrounded by clean water. The plants are healthy and usually grow much quicker because they are receiving as much food as they want every hour of every day. Some of the inputs required for this system to work is electricity to run a pump, fish food, and sometimes additional oxygen from a pump. The fish food however can be generated from an additional sub-system where even the fish food is part of the continuous flow.
A more detailed explanation
You don't need to understand more than the simple explanation above to get started with Aquaponics. However, more information certainly makes it easier to get this running and helps you know more about how your system actually works. This system, built correctly, takes advantage of the blue prints found in nature for converting fish waste to plant food. The primary concept to be learned in this cleaning process is called the Nitrogen Cycle.
Nitrogen is an essential element necessary for life on Earth as we know it. The Nitrogen Cycle is a series of chemical processes whereby nitrogen from the environment is consumed by living organisms and processed into various different nitrogen-based chemical forms. This is accomplished via a chain of living organisms, each utilizing nitrogen in some way to live, and converting it into another nitrogen-based chemical structure which is then needed by another organism. In this way, nitrogen is continually cycled from the environment, through the biological system, and back into the environment.
This diagram illustrates the various stages of the overall nitrogen cycle in our environment. In Aquaponics, we are only concerned with a portion of this cycle, and we begin the nitrogen cycle at the Ammonium stage (NH4+) since that is what is directly excreted by our fish. Fish waste, (NH4+), is taken advantage of and is the raw material from which plant food is produced. As can be seen in the illustration above, ammonium is only two chemical steps away from being fully edible plant food, or nitrate (NO3-). What it needs to be converted into nitrate is to be processed by two types of bacteria referred to as nitrifying bacteria. One type of nitrifying bacteria converts ammonium (NH4+) into nitrite (NO2-), and a second type of nitrifying bacteria converts nitrite into nitrate (NO3-).
Nitrifying bacteria are present almost everywhere in our environment, at some level, and they will be present, though at low levels, in any gravel used for grow beds. Once these bacteria start receiving ammonia-rich tank water on a regular basis, they will multiply and start converting ammonia into nitrite and then nitrate. In a fully balanced system, which takes 6-8 weeks to develop, your grow bed bacteria will be producing tremendous quantities of nitrate. This will allow your plants to grow and will keep your fish water clean. Once this stage is reached, the system is said to be “matured,” and it pretty much keeps itself balanced, with very little maintenance required.
- Very low maintenance
- Very high density food production. Regular plant-spacing rules don’t apply because roots do not need the room they need in regular planting.
- Can be scaled to work in areas as small as apartment balconies to large commercial production facilities.
- Produces plants as well as animal protein (fish).
- Allows for very high fish stocking densities.
- Uses very little water: once the system is going, you only need to replace water lost through evaporation and transpiration of plants.
- All plant food and “fertilizers” are organically produced – by your fish. No need to deal with hydroponic nutrients or fertilizers, and more importantly, there is no need to be dependent on someone else’s production of these things (which by the way are a marvel of the oil age only).
- Eliminates waste produced by aquaculture systems.
- Avoids waste produced by regular hydroponic systems (including water waste).
- In addition to the gravel grow-bed system, there are continuous-flow systems (aka floating-raft) for much higher-throughput and potential commercial or community-based production.
- Moderate to high start-up costs. You’ll need a fish tank, at least one main pump as well as a power-failure back-up pump, grow beds, etc. You may also wish to enclose your set up in a greenhouse.
- In very cold climates, you may have to heat your water. This could pose a serious disadvantage, but is surmountable.
- Monitoring PH, ammonia, and nitrate/nitrite levels is very important and in the start-up phase (first 6-8 weeks) can be tedious as you’ll have to test daily. Once the system matures, levels of all these variables will stabilize and monitoring them becomes a weekly task done in under 20 minutes.
- AP systems have one critical failure point, which is your water pump. A battery back-up system is required, otherwise your fish will all die due to lack of oxygenation upon your first significant power outage. These back-up systems are not complicated, but they do represent an additional expense.