Aquaponics at Windward

A curious and colorful Tilapia in our dinning-hall fish tank, 2012.

Aquaponics combines aquaculture (the growing of aquatic organisms) with hydroponics (the growing of vegetables in a soilless medium), thus imitating the natural dynamics of freshwater ecosystems.

Aquaponoics systems have many benefits in the context of a rural village on marginal land, and for people with limited access to fresh water. A well-run aquaponics system can produce the same amount of quality food, in the form of fish and vegetables, while using 1/10 of the water traditional soil-based agriculture uses.

Windward has two outdoor aquaponics systems currently in place, and our goal is to integrate a large aquaponics system into an insulated greenhouse that will enable us to grow tilapia (a resilient warm water species of fish commonly used in aquaponics systems) by using the thermal mass of the water in the aquaponics systems itself as a thermal buffer against the cold temperatures during the winter months. This will also allow us to continue to harvest vegetables and fruits throughout the winter.

The Basics

Aquatic animals like fish, snails, crawdads and muscles produce nitrogenous ammonia (NH3). The ammonia is then converted into nitrite (NO2-) by Ammonia-Oxidizing Archea and Ammonia-Oxidizing Bacteria. Nitrite is then converted into Nitrate (NO3-)by bacteria in the genus Nitrobacter

duckweed, a high protein aquatic plant we're using in our aquaponics systems

This process of converting ammonia into nitrites and then into nitrates is called nitrification and is a fundamental part of the nitrogen cycle in terrestrial and aquatic ecosystems.

Once the nitrogenous animal wastes have been converted into nitrate, they are in the appropriate form for plant roots to take up.

The plants transform the nitrates into proteins and leafy green-ness, and in the process help to relieve the water of high levels of nitrates which could negatively impact the plants.

This means that in designing an aquaponics system we need to create appropriately scaled habitats for aqautic animals, aerobic bacteria, and plants.

Windward's Aquaponics

Step-by-Step Learning

Intern Virgil helping to contruct the first iteration of barrelponics in '07

Setting up a well functioning, community scale aquaponics system is a complex task. In pursuit of the final goal, we've taken many gradual steps to grapple with the dynamics of all the individual pieces.

Our smaller systems have helped us learn about nutrient cycling dynamics, potential water flow issues with different pumps and piping configurations, how to scale the system for adequate plant productivity and ample bacterial populations, as well as some demonstration of the thermal buffering effects of large quantities of earth sheltered water effectively extending the growing season.

In 2011 we got our first Tilapia and started to learn about general care, the effects of water chemistry variation on fish health, tilapia behavior, social dynamics and breeding, and how to protect the fry from predation by adult fish. We still have much to learn about the best practices of raising tilapia.

While we learn about the fish, bacteria and plants, we are also constructing the integrated earth-sheltered greenhouse that will eventually house a mature, community scale aquaponics system.

Barrel-Ponics in late winter 2011, notice the fish tank at the bottom.

We currently have two operating aquaponics systems, and one that is under construction.

1.) "Barrel-Ponics"

A small system with about sixteen square feet of grow beds and a 100 gallon fish "pond".

Barrel-ponics has operated well since 2007 with little to no maintenance. We have tried out many types of plants in the system - from collard greens to chives, tomatoes to mint- all of which did relatively well. The system was built in a relatively shady area, so some of the heat-loving plants like tomatoes grow poorly primarily due to shade.

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Constructing of "Duck-Ponics" system in '07

2.) "Duck-Ponics"

"Duck-Ponics" is a medium scale system with about 200 square feet of grow beds and about 1200 gallons of water in the form of a concrete duck pond. The duck pond is gravity fed by a large tank that receives the overflow of our main potable water tank. Excess "green water" from the duck pond travels via siphon hose to a holding tank where it is used to irrigate plants in the main garden.

The Duck-Ponics system has evolved continuously since 2007 when it was first installed. It's a simple and incredibly resilient system that has been cranking out vegetables year after year, and providing liquid fertilizer for our gardens and food forest, all the while giving the ducks a place to splash and play.

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3.) The Pearl

Opalyn and Apprentice Jeff setting up concrete forms for the Pearl, 2012

The Pearl is the insulated greenhouse, currently under-construction, that will house the integrated aquaponics system.

The Pearl is much more than just an aquaponics system. It is a whole greenhouse system designed to be able to provide year round warm temperatures for Tilapia culture. The greenhouse will feature several thousand gallons of water capacity, fishfood insect breeding quarters, solar refrigeration and ice house capacity on the north wall, and as much plant grow space as we can manage to cram into the building.

Right now we are pouring the concrete, and finalizing the details for the inner working of the system.

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Protoculture and Producing fish food

One of the most essential parts of a sustainable system is being able to prodcue all the inputs needed for that system. Because aquaponics is an integration of hydroponics and aquaculture, the "waste" of either component become food for the other. This goes a long way to reduce the need for inputs, but does not eliminate it.

As the saying goes, "There ain't no such thing as a free lunch", and we still need to feed the fish. This is one of the most important steps in developing a self-sustaining aquaponics system.

BSF larva, 2011

Typically, fish food contains approximately 40% protein, a feed quality such that fish like tilapia are able to convert about 1.2 pounds of commercial quality food into a pound of fish. Even if you have to buy your fish food, that's an impressive return.

Mature tilapia are also able to live and grow on a diet based on plankton and aquatic plants however, growing Tilapia need a higher protein diet to grow fast enough to achieve a sizeable annual harvest.

This is why we are simultaneously developing our insect breeding program. The primary insects we are working with are red-wriggler Earth worms and Black Soldier Flies.

Find articles about BSF and Earthworms

Come Work With Us

Looking for more experiential learning as it relates to Aquaponics? Consider joining us for a season or a life time. Get Involved.