Aquaponics

Aquaponics

Simple Aquaponic System

Aquaponics ist a sustainable food production system that combines a traditional aquaculture (raising aquatic animals such as fish, crayfish or (prawns in tanks) with hydroponics (cultivating plants in water) in a symbiotic  environment. In the aquaculture, effluents accumulate in water increasing the toxicity for fish.  This water is run through a hydroponic system where the by-products from the aquaculture are filtered out by plants to be used as vital nutrients  after which the cleansed water recirculates back to the fish tank.

Nitrogen Cycle

Monitoring water quality is an essential component of the aquaponic system.  The nitrogen cycle,  or cycles in general, are difficult concepts for students to visualize. Nitrogen access is a very important part of the aquaponic system because it provides nutrients for the plants.Fish produce waste through fecal production or the excretion of ammonia. ammonia is converted into nitrite which is then converted into nitrate.  Nitrate is a form of nitrogen accessible by plants. Ammonia and nitrite are toxic to fish at low levels.  In a natural system, nitrate is not  usually a  problem but in a closed system such as you do need to monitor the amounts.  Increased levels are needed for plant growth but have to be balanced with levels that fish can safely tolerate

This year the aquaponics team went from a very simple system used for demonstration to a more complex system using a grow bed.  This system uses an ebb and flow design  with a sump.  The emphasis on this project  however is not the aquaponic system  but rather the control systems used to feed fish and monitor temperature and pH.  

Once you decide what you are going to build the next step is shop.   We went to Lowe's to see if  we could all the parts to build our system.  This is an important part of the project.  Whether it is teachers or students it is important for them to be part of the process from design to construction.  As we were buying different PVC parts Fern Edwards asked me how I knew so much about PVC?  I didn't when I started - I knew it was white and used for plumbing.  But after many conversations with Lowe's employees and trial and error I got better.  The hands-on approach really does work!

Once you get your supplies the next step is to  build your design.  The design that was chosen was a 30 gallon tub for fish,  10 gallon tub for plants and another 30 gallon tub for a sump.  Since water runs downhill the fish tank would be highest and drain into the plant tub. A ebb and flow siphon would be designed to drain into the sump.   

The building and maintaining of the automatic siphon has been the most challenging part of the project.  We ended up modifying our original design but still find it has to be tweaked on a daily basis.  One other problem we have had to deal  with is fish getting stuck in the bulkhead  that allows water to leave the fish tank and move to the plant tank.  This will dramatically impede flow.  Another problem that affected the autosiphon was clay pebbles slipping under the outer wall of the siphon and building up so that it didn't drain properly.  Still researching different way to do it. It will work fine for awhile but them the ebb and flow slows down.

The next step once the aquaponic unit is working is to start building the control system.