The tomato, the bacteria and the fish poo.

Every now and then there is an idea so pregnant that you have to pinch yourself. Aquaponics is one such idea.

At its heart are beneficial relationships between fish, nitrifying bacteria and plants. Put simply: fish poo feeds the nitrifying bacteria and plants and in return the nitrifying bacteria and plants clean the water for the fish. The water from the fish is recirculated through gravel-filled grow-beds and then back in with the fish.

A wide range of vegetables and herbs are grown in the grow-beds. Aquaponics is a polyculture of edible fish and plants, not a monoculture of one or the other. The fish support plant growth and the plants support healthy fish.

Onto this basic framework of fish, bacteria and plants, other organisms can be added. Worms, for example, thrive in the moist conditions within the grow-beds. Worms fullfil a number of useful roles: preventing the grow-bed gravel or media from clogging up, facilitating the absorbtion of a fuller range of plant nutrients via the fungi, enzymes and hormones in their digestive tracts and decomposing dead plant material. In addition to this, they also become an important product to harvest in their own right as fish feed. With the presence of worms we therefore have the real potential for the system itself to meet the nutritional needs of the fish and become truly self-sustaining.

The benefits of aquaponics are significant:

The cost and work of applying fertilizer to the plant crop is removed or almost non- existent.

Aquaponics is essentially organic. An application of pesticide to the plants would adversely affect the fish and vice versa.

Water is recirculated and so conserved. By comparison the irrigation of soil-grown crops is very wasteful of water as much is lost to evaporation and leaching.

Aquaponics is highly productive. The conversion of food into flesh by growing fish far exceeds what is possible for poultry, pigs, sheep and cattle. Grazing beef cattle
will require more than 7kg of feed to produce 1kg of body mass whilst fish such as Tilapia only 1.2kg of feed will produce 1kg of weight gain.

Vertical space is made good use of in aquaponics as grow-beds can be supported above the fish tanks. Indeed, several tiers of grow-bed are not uncommon.

Like other forms of sustainable freshwater aquaculture aquaponics is able to meet demand for fish without depleting wild marine fish stocks.

Edible Landscape is working on a back yard aquaponics system informed by permaculture ethics and design principles. The nutritional needs of the fish will be met by the system and from within the garden itself. In addition the electricity required for the pumps will come form renewable technologies.

We will add pictures and updates to this page as the project develops.