Aquaponics: Summer 2013 Master Gardener Newsletter

A small, portable aquaponics system. Photo by Charlie Vinz.
A small, portable aquaponics system.
Photo by Charlie Vinz.

A new style of vegetable gardening is becoming popular in many parts of the country called aquaponic gardening. Aquaponic gardening is growing vegetables and fruits in a soilless environment using the waste water from fish tanks as a nutrient source. Your harvest can include both vegetables and fish, providing a healthy source of protein and an abundance of antioxidant-rich vegetables. A recent study showed that the Mediterranean diet is good for your heart. Characterized by healthy fat sources, including fish and olive oil, and lots of vegetables and fruits, it is possible to “grow” a Mediterranean diet right in your own backyard using aquaponics.

Aquaponic gardening is the marriage of hydroponics, growing plants in soilless culture, with aquaculture, cultivation of fish for food. Neither system alone is fully sustainable because the waste water must be discharged or treated to get rid of nutrient buildup and waste products. Combined, as they are in aquaponics, the plants act as biofilters for the fish and the fish waste is happily used by the plants as fertilizer.

Think your veggies from an Aquaponics system will taste “fishy”? Not so! The population of beneficial bacteria that builds up in the system converts ammonia from the fish waste into nitrate, which is easily taken up by plant roots. No part of the fish or its waste ever ends up in your plants. The solid waste is most efficiently decomposed by composting red worms, which are added to the growing medium.

What about fish nibbling on the plant roots? This doesn’t happen either because fish and plants are grown in separate containers connected by plumbing that circulates the fish water to the plant grow beds. Once filtered by the plants, the water is recirculated back to the fish tank, re-oxygenated and stripped of the ammonia that is toxic to fish.

Many types of aquaponic systems exist, ranging from an indoor system with an aquarium and simple grow bed to outdoor systems protected by a greenhouse or hoop house and powered by the sun. In our northern Nevada climate, indoor or greenhouse-based systems are best because most fish won’t survive our winters outdoors. The easiest method is to grow plants in a coarse soilless medium, such as gravel or expanded shale, flooded periodically with water from the fish tank. This simple ebb-and-flood system can also become a home for composting worms which, along with the beneficial bacteria that build up naturally in the system, break down the ammonia waste to a form plants prefer.

A big selling point for aquaponic gardening in our climate is that these systems use very little water. The only water lost in the process occurs by evaporation from the tanks or transpiration through the plant leaves. The only inputs to the system include food for the fish and a small amount of water to top off your tanks.

The most common fish used in these systems include trout, arctic char, bass and some species of perch and catfish. An annual permit from the Nevada Department of Wildlife is required to raise these fish, and an importation permit may be needed if they are obtained from out-of-state. Visit http://www.ndow.org/law/licenses/ for information on possession and importation of wildlife for commercial and noncommercial use.