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Wednesday, April 24, 2013

Pros and Cons of Different System Types

Commercial Aquaponics


I've been trying to compare the pros and cons of different types of aquaponic systems recently.  Right now, I'm working on constructing a 105 gallon setup at my friend's apartment.  We're making a simple flood and drain system, with a 50 gallon grow bed.  Filling that grow bed will require almost 200 Liters of expanded clay or some other media.  All that media is going to double the cost of our system.  We were thinking about alternative methods, such as expanded shale or even something like legos (but we don't have nearly 50 Gallons of legos).  The cost of buying a grow media for a large grow bed is so high, that it really got me thinking about alternative systems.  Here's a list of pros and cons of various aquaponic systems.  If you know anything that I haven't listed, please leave a comment and I'll add it to my list and credit you.


Media Bed Systems
Chift Pist, Simple Flood and Drain (Ebb and Flow), Constant Flood (Continuous Flow)
Pros
· Self Cleaning - The grow media filters out the fish waste
· A media bed performs three (3) filtering functions:
    · mechanical (solids removal)
    · mineralization (solids breakdown and return to the water) 
    · bio-filtration
· Media provides better plant support and is more closely related to traditional soil gardening because there is a media to plant into

Cons
· Expensive growing media

A Typical Media Bed


Chift Pist
Pros
· Pump is in sump tank away from fish and wastes
· Water level in fish tank remains constant
· Great if you have a tall fish tank
· Larger water volume because of sump
Cons
· Extra equipment required (sump tank)
· Must have tall fish tank or stand
· Can take up larger footprint

Chift Pist system


Simple Flood and Drain / Ebb and Flow
Pros
· The grow bed can be separated from the fish reservoir
· Simple design - Only two major system components - lower cost
· It is easy to understand and learn
· Great if you have a tall fish tank
Cons
· Requires a timer or bell syphon
· Pump is in fish tank, exposed to fish and waste
· Water level in tank fluctuates a little


Simple Flood and Drain system


Constant Flood / Continuous Flow
Pros
· Same as the Simple Flood and Drain, except when you remove the timer, the system is constantly flooding
Cons
· Pump is in fish tank
· Plant roots can become waterlogged, and areas of the grow bed can become stagnant and anaerobic as the flow of fresh water through the bed moves around any blockages


Constant Flood system


Deep Water Culture (DWC)
Pros
· Resistant against water temperature and pH fluctuations
· Excellent root development due to easy access to oxygen
· There is plenty of surface area for the beneficial bacteria to grow
· Very good for lettuces and leafy vegetables – used extensively by commercial farmers
Cons
· Requires additional filtration to remove solids
· Large plants such as tomatoes, cucumbers, etc. can be difficult, if not impossible, to support


Deep Water Culture system


Nutrient Film Technique (NFT)
Pros
· Both components (fish and plants) may be decoupled from each other whenever required and can/do operate independently of each other if required.  I believe this is important in a commercial situation because it allows fish or plant production to continue when and if there are any problems with the other component
Cons
· Water susceptible to temperature fluctuations
· Requires additional filtration to remove solids
· Roots that die and detach from plants can cause blockages in water flow
· NFT is only really suitable for certain types of plants, generally leafy green vegetables, larger plants will have root systems that are too big and invasive, or they become too heavy for the lightweight growing gutters

Nutrient Film Technique system







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