The aquaponics system exhibited as part of Waiting Room at Survival Kit / Umeå 2014 is a simple ebb and flow system. Water is pumped up from the aquarium to the grow bed by a small pump. The water fills up the grow bed until the water level reaches the overflow protection (flood). As long as the pump is pumping the grow bed stays filled with water. When the pump stops the water flows back through the pump into the aquarium and the grow bed is dried (ebb).
All plants in the aquaponics system are edible and many of the plants have special nutritional properties and tastes. The plants growing to the far left in the grow bed are watercress (Nasturtium officinale). Watercress is a rapidly growing aquatic or semiaquatic plant. It is one of the oldest known leaf vegetables consumed by humans. Watercress is rich in omega-3, minerals and vitamins. Other plants growing in the grow bed are red basil (Ocimum basilicum), miner’s lettuce (Claytona perfoliata), green purslane (Portulaca sativa), minutina (Plantago coronopus), and various plants of the Brassica genus.
The plant growing on the water surface in the aquarium is duckweed (Lemna minor). Duckweed can grow very rapidly and often form thick carpets over bodies of water. It is rich in protein and fats. Duckweed is grown commercially as animal fodder but also has potential as food for humans. It tastes fresh and can be used on sandwiches and in salads.
Under the water surface grows lemon bacopa (Bacopa amplexiculis / Bacopa caroliniana) and water hyssop (Bacopa monnieri). Lemon bacopa’s taste is reminiscent of lime and thyme. It can be used as a seasoning, in salads and to make tea. Water hyssop has traditionally been used as a cognitive enhancer in Ayurvedic medicine. It is currently being studied for its possible neuroprotective properties. Health products with water hyssop are claimed to enhance memory development, learning, and concentration, and to provide relief to patients with anxiety or epileptic disorders. Water hyssop is also said to be good for Alzheimer’s and to calm the mind. Its taste is bitter.
The aquaponics system has been assembled with sustainability and food safety in mind. Not all components are the optimal choices but most of the components used are non-toxic, (relatively) locally produced, recycled, or recyclable.
The seeds from the plants grown in the grow bed were bought from Swedish ecological seed stores. Both Bacopa species were bought in a local aquarium store. The seller didn’t know where they originated from but they are most likely from Denmark. The duckweed was gathered from a local pond.
The gravel in the aquarium was sourced from a local gravel pile and washed thoroughly. The pots are made in Sweden from Swedish clay. The plants are planted in the pots with ecological soil and gravel on top. The soil provide nutrients to the water plants and the water. The gravel prevents the soil from spilling out and dirtying the water.
The blue tray has been reused from a previous project. It is made out of HDPE, a food safe plastic. The aquarium was bought new at a local aquarium store. Its origin is unknown. The lighting armatures are IP65 classified, meaning that they are protected from water splashes. Each armature uses two 14 watt fluorescent tubes. The tubes are on for 14 hours per day and should last for more than four years. The pump consumes 4.5 watts. The grow bed is flooded for 15 minutes every hour. In total the pump runs six hours per day. The pump has a three year warranty, hopefully it lasts longer. Total energy consumption is approximately 296 kWh per year.
The growth media in the tray is expanded clay pebbles produced in Sweden. The pebbles were washed thoroughly to prevent clay dust from clouding the water. Expanded clay pebbles was chosen instead of gravel because of their light weight. The installation was transported from Stockholm to Umea as carryon luggage on the train.
Nitrifying bacteria used to “cycle” the aquarium was bought at a local aquarium store. This would not have been necessary but was used as a precaution to increase the chances of the system working properly in time for the exhibition. Cycling is the process during which bacteria that convert ammonia (waste from fish, fodder and plants etc) to nitrite and finally to nitrate (plant nutrient) is established in the aquarium. Ammonia is poisonous for fish and fish should not be introduced in an aquaponic system before bacteria that can deal with the ammonia produced by the fish have established. Without introducing nitrifying bacteria through commercial products it can take over a month for the bacteria to establish.
The aquaponics system is provided with liquid fertiliser for planted aquariums. The fertiliser was bought at a local aquarium and its origin and exact content is unknown. Eventually attempts will be made to use compost as fertiliser and possibly kitchen scrap as fodder for worms or fish. At the time of writing there are snails and other small critters living in the aquarium. They came into the aquarium with the duckweed and seem to have established themselves well. The possibilities of introducing more animals, such as fish and worms, are investigated with concern for the animals wellbeing in mind. If more animals are introduced into the system they will be introduced to create a more diverse and productive ecosystem and not to be eaten.