The Primary Facets of Aquaponic Gardening


Aquaponic gardens come in myriad shapes and sizes.  They are as varied as the varieties of fish and plants that can grow within them.  In fact, one of the biggest benefits of aquaponics is the adaptability and versatility of each unique garden. Aquaponics grows steadily, from desert climates, such as Tucson and Israel, to snowy climates such as our own farm here in Connecticut.

Right now, under today’s snowfall, our systems purr on.  You can hear the gurgle of water over the muffled falling of snow.  Systems can run on flat land or on sloped land.  In fact, uneven land even allows inventive engineers to use gravity, rather than electricity, to move the water in their system.  Aquaponic gardens can range in size from desktop to thousands of square feet.  In fact, the first system we ever made sat right on my desk in our Boston apartment, way back before FRESH Farm was even an idea in our heads.

With all of this exciting variety, it can be a little hard to wrap your head around just what an aquaponic garden consists of.

Aquaponics is the joining of aquaculture and hydroponics.  In a very general sense, all aquaponics gardens consist of three components:

  1. A fish tank with fish [the aquaculture]
  2. A plant bed with plants [the hydroponics]
  3. Plumbing between the two and a way to move the water [the connection]

Everything else is simply to augment the function of those three main components.

In order to get a broad spectrum view of aquaponics, let’s briefly look at each of these components:

The Fish Tank [aquaculture]:

Aquaponics Aquaculture Tank
Aquaponics Aquaculture Tank

Fish tanks can come in nearly any shape under the sun.  There are the classic acrylic/glass aquariums, large plastic tubs, or in our case, upcycled oil tanks lined with pond liner.  As long as it is food safe and able to hold water without leaking, it can be a fish tank.  Although most desktop aquariums are entirely see through, most fish tend to like shade more than light, so it is helpful if the tank is a dark color.  This also helps to inhibit unwanted algae growth.

Within the aquaponics industry, a common ratio for fish tank to plant bed size is 1:3, or for every 1 gallon of fish tank water there is 3 cubic feet of space in the grow bed.  What this means is that you will have three times more water in the grow beds than in the fish tank at any given time.  Depending on the fish stocking density, it is relatively safe to go all the way to a 1:1 ratio, of 1 gallon fish tank water to 1 cubic feet grow bed space.  Take this into account when selecting your fish tank, as you want it to fit appropriately in the space you have, alongside the grow beds.

Typical aquaculture requires large, expensive filtration systems in order to keep the fish tanks relatively clean and free from disease.  One of the benefits of aquaponics is that the cost of aquaculture filtration is transformed into the benefit of an additional production stream, the plant beds!

 

The Plant Beds [hydroponics]:

Plant beds are a bit more complicated topic.  Just like there are many styles of growing in soil, there are many styles of growing in hydroponics.  The five main, overarching styles are:

  1. Deep Water Culture (DWC)
  2. Media Beds
  3. Nutrient Film Technique (NFT)
  4. Vertical Growing
  5. Hybrid Style

Deep Water Culture (DWC), also known as raft beds, is most commonly in use in large scale, commercial type systems where economies of scale come in to play.  A series of water-tight troughs, generally one foot deep, resembles a large stream being fed by the fish tank.  Raft beds float on top of the trough water.  Holes are drilled in each raft at specific locations and in each hole is placed a net pot with a seedling.

A net pot is a little black planting pot with large holes in it, which allow the roots to drape down into the water below the raft. The rafts float lazily along the filled troughs, while the roots below are busy filtering the passing water.

This style of garden is great at growing leafy greens of all types as well as most herbs, like basil, oregano, chives, and others.  DWC can even grow melons!

Currently most rafts are made from styrofoam board.  This is perhaps the least organic thing about aquaponics to date, industry wide.  We are currently researching more organic alternatives to styrofoam rafts.  If you have any ideas we are happy to discuss, please contact us.

DWC also requires additional filtration for removing solids.  The lackadaisical pace of the water does not provide adequate filtration for the heavier solids produced by the fish.  This can prove to be a boon however, as you can siphon off the resulting solids to create an enormously potent fertilizer concentrate.  We are currently designing a system to do this, which we will install this spring.

Also, in order to make sure that plants don’t drown, DWC beds must be aerated, much like a fish tank.  This is one of the limitations on the types of plants you can grow in DWC.

Media beds are the easiest method of growth on a small to medium scale.  Our Conscious Family Garden is an entirely media bed garden.  The name media bed refers to the growing space, which is filled with a growing medium, or media.  Examples include expanded clay (hydroton), expanded shale, volcanic rock, and gravel.  A porous, (usually) inert media is most desired.

A higher porosity allows for more water absorption, nutrient retention and provides a safe living quarters for the beneficial bacteria within the system.  The media can be thought of as a city for these beneficial bacteria, allowing for a higher degree of sophistication and habitation.  The bacteria have a solid home from which they are able to reach out and convert nutrients into available forms for the plants.

The media also provides a place for the roots of the plants to anchor on to.  Due to this fact, media beds are able to grow the widest variety of plants of any aquaponic system.  FRESH Farm has grown rosemary, oregano, sage, lavender, jalapenos, strawberries, green beans, tomatoes, peppermint and chocolate mint, lettuce, genovese basil, thai basil, purple basil, and boxwood basil.  We are even currently growing a dwarf j
asmine tree and a real green tea tree!  The bouquet of aroma and color of a flourishing media bed is a true wonder to behold.

aquaponics-media-bed
An example of an aquaponics media bed.

Media beds offer more benefits beyond the wide variety of plants.  Red-wriggler worms love living in media beds!  These gardener’s best friends help to break down fish solids deposited in the media beds into forms that are very easily absorbed by the plant roots.  Worms also harbor some of the most beneficial bacteria to plant roots, increasing the overall productivity of your plants!  Therefore, media beds allow for increased solids filtration and benefits from increased nutrient absorption and heightened productivity!

Media beds typically operate on an flood and drain cycle, also known as ebb and flow.  To start off a media bed cycle, water flows into the media beds from the fish tank, which is the flood, or flow, cycle.  Then once the water hits a specific level, it empties out of the media bed, this is the drain, or ebb cycle.  The water moves from the media beds either back to the fish tank or to the sump tank.

A secondary component to most media bed systems is the sump tank.  The sump tank is a secondary water container, generally ⅔ the size of the fish tank itself.  Sumps really become necessary once you are talking grow bed sizes over 50 gallons, you simply don’t want to displace that much water from your fish tank all at once.  The sump acts as an intermediary in the system, allowing the fish tank’s water level to stay stable while the grow beds flow in and out in their ebb and flow cycle, emptying into the sump.  The sump is typically the lowest point of any system, for this reason the sump generally houses the pump in a media bed aquaponics garden.

 

A typical full cycle of a media bed garden runs like this:

Fish tank -> Media Beds -> Sump -> Fish Tank -> Media Beds -> Sump -> …

The water can flow from the media bed to the sump through many different means.  There are slotted drains, which consistently flow while varying their rates.  These can be manipulated into creating a flood and drain system by placing a fast draining slot up high, with a slow draining slot down low.

We prefer another method, known as the bell siphon.  It takes advantage of the physical phenomena of the vortex in order to flush the entire grow bed in seconds.  An upside down cone shaped drain pipe is surrounded by a cylinder with a closed top.  This creates an airtight seal around the drain pipe.

As the water in the bed rises above the level of the drain, it rushes down.  This is where it gets fancy, the water is actually sped up in its fall down the drain due to the cone shape of the drain pipe, a result of Bernoulli principle.  This increase in drain speed will rush water down the siphon exit, which leads to the sump tank.  As the water releases out of the end of the siphon, it will take with it all of the air inside of the airtight drainage pipe.  This will have the effect of suctioning out water until air is able to enter the airtight drainage pipe.

Therefore a vortex siphon works like this: the water is pumped in, the water level rises in the bed, it reaches the tip of the drain pipe and flows over, the water rushes down the drain and exits into the sump, the air is carried with the water, which creating a vortex, the rest of the water in the grow bed follows the pull of the vortex, as the water level lowers due to the draining, air eventually hits the entry points into the sealed airtight drainage pipe.

This air is all it takes to break the vortex effect, stabilizing the water level and allowing the bed to fill up once again.  This effect is really something to see in person.  The bed can take more than 15 minutes to fill and the vortex siphon will empty it in 30 seconds!  This has the benefit of also adding oxygen to the water as it is flushes out.  The massive turbulence caused by the vortex siphon creates an outstanding level of oxygenation.  The rapid draining of the media beds also increases oxygenation. The air is sucked down to replace the draining water.

Nutrient Film Technique (NFT) is very popular for strictly hydroponic setups, but falls short for aquaponic production.  NFT is when plants are growing in long, small beds, typically made from pvc piping or a gutter-like material.  Water is feeds through these pipes, which wicks up to the plant through the nutrient film, another word for growing media.  These systems work very well for hydroponics, which does not typically have heavy solids to deal with.  Unfortunately, aquaponics must reckon with the solids waste produced by the fish.  This is a valuable resource when dealt with properly, but becomes a downright nuisance if it is ignored. If you address the solids NFT aquaponics will make more sense.

A newly flourishing style of hydroponics, known as vertical growing, is a very interesting phenomena.  It refers to the practice of growing produce in towers, similar to an NFT system hung up vertically.  Nutrient water is comes in from above and drips down the tower, via gravity, feeding the plants along the way.  As with all aquaponics, the idea is that each plant will simply take its fill, and due to the abundance of available nutrients, will pass on the rest of the nutrient laden water for the next plant.  Therefore, no matter where on the tower, the plant will receive optimum nutrition.

This style is very useful for integrating with the other methods of growing aquaponically.  One of the first commercial gardens I ever saw integrated vertical systems with their raft beds and greatly increased their production capacity.  Vertical growing tends to increase planting efficiency and therefore production capacity because you can grow more plants per square foot of space.

Just as commercial growers are more seriously considering the integration of vertical growing into their systems, many aquaponics gardens benefits from a hybridization or diversification of growing methods all within a single system.  As in nature, diversity brings strength and resilience to any aquaponic garden.  An example might sound like this: a fish tank feeds to media beds, providing solids filtration for the raft beds, which then pump up to the vertical towers which drip back down directly in to the fish tank.  This represents an integration of nearly all the methods of hydroponic growing into one hyper-efficient ecosystem.

We believe this hybrid growing style is the future of food and will provide one of the many answers necessary to address hunger today.

The Plumbing [connection]:

Compared to the fish tank and plant beds, the plumbing is relatively simple. The broad view of plumbing is ‘a connection between the fish tank and the plant beds’. Under this view, anything which carries water and is food safe we can use for plumbing.  Traditional examples include bamboo and ceramic piping.

Most aquaponic gardens todayHaber-Bosch-Engine use standardized schedule 4 PVC piping.  PVC is food safe, builds like legos and holds up in almost all aquaponic situations and environmental conditions.  There is an incredible array of pvc pieces in scalable sizes for any project.

This variety allows the inventive aquaponeer to adapt their aquaponic garden to every situation!  Look for in depth plumbing tips and tricks in future blog posts!  Here’s one to tide you over: make gravity work for you!  Yo can place either the fish tank or plant beds above the other. Then you can harness the power of gravity to move the water for you, free of charge!  This technique, applied properly, allows for a single pump to run any sized system, even the largest aquaponic gardens!  Keep this in mind, should you decide to design your own garden.

We’ll be breaking down each individual component in greater detail in later blog posts and books online in order to make it crystal clear how and why each component is necessary to the overall health of the system. Just as in nature, all the elements of the ecosystem must find and maintain balance.

The Trifecta team.


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