“Aquaponics is the cultivation of fish and plants together in a constructed recirculating ecosystem utilising natural bacterial cycles to convert fish waste to plant nutrients. This is an environmentally friendly, natural food-growing method that harnesses the best attributes of aquaculture and hydroponics without the need to discard any water or filtrate or add chemical fertilisers” – Aquaponic Gardening Community, November 2010
How it works –
- Urban areas create waste
- We turn that waste and add some more ingredients to make sustainable fish feed
- The fish eat the feed
- The waste from the fish and any leftover food accumulates in the water because fresh water isn’t flowing in – we are pumping the same water around the system all the time.
- Nitrosomonas bacteria in the water convert the ammonium in this water to toxic
nitrite, then nitrobacter bacteria to nitrate which is an essential nutrient for plant growth.
- This effluent rich water is pumped from the fish tanks to the plant beds where it provides food for the plants. In our project we use a hydroleca substrate in part of our hydroponic beds, inhabited by a family of worms that eat the fish solids that accumulate in the beds, and make it more useful to the plants. So the plants clean the water
- As the water flows back into the fish tank its splashing disturbs and oxygenates the water.
- And we produce fish and plants for eating!
Ins and Outs – The three main inputs to our system are water, feed for the fish and energy to power the lights, pumps, biofilters and heaters. We also introduce the baby fish (fry) and plants. The main outputs from our system are fish and plants, but sometimes we may get an accumulation of fish solids that we can add to our compost.
Sensitive ecosystem – The system relies on the relationship between the fish, bacteria, worms and plants to maintain healthy ecosystems for each of the species. Water is only added to replace losses from absorption into the organisms, transpiration by the plants and evaporation from the tanks. As a result the system is very water-efficient compared to conventional vegetable production
What Species? – In the Unit 1 Vale Lane facility we plan on working with Bristol Water to help with Eel conservation – so thats the fish we have in mind for our system at the moment. We also want to grow some crayfish. At Phoenix cafe we use ornamental Koi Carp. In our Pilots we used Tilapia. You can grow any fish bar Salmon and Cod in an aquaponics system – Cod and Salmon need very fresh and cold water, so are not well suited to the recirculating systems for some parts of their life cycle. The most popular fish to grow in aquaponics is Tilapia because of its high tolerance range of Ph, temperature, oxygen and dissolved solids – its a hardy fish. In Australia Barramundi and Murray Cod are more common.
With regards to plants, leafy greens that thrive on nitrates are the most commonly used, however you can also find systems that grow tomatoes, peppers, cucumber, even turnips! In our project we plan on growing watercress and wasabi as these are cold weather tolerant with low light needs. But we’re sure to mix in some other fun crops too!
Where can it happen? – Aquaponics is used as a production technique across the world. It is currently more commonly practiced though in warmer climates – Australia, Thailand, Bangladesh however there is a growing amount of companies undertaking aquaponics in cooler climates. In Iceland, company Matorka is producing tilapia using geothermal heat, and more companies are starting up in north America like The Plant in Chicago. Equally aquaponics farms are quite large scale operations, so aquaponics on a commercial scale takes place in rural areas, however there are people investigating the options for urban aquaponics. Companies such as The Plant in Chicago, Growing Power and Sweet Water Organics in Wisconsin are leading the way in urban aquaponic production
Viability– Aquaponics sits under the category of integrated multi-trophic aquaculture – (that is if you come at it from the aquaculture side rather than the hydroponics side). The viability of IMTA is not really in question. However the viability of aquaponics itself (although a form of IMTA) attempts a more whole-system approach; with as much attention on the hydroponic aspects as the aquaculture aspects and is still the subject of research. Many of the businesses that consider themselves to be ‘aquaponics businesses’ are less that 10 years old; to date some are profitable, and some are not. Many are diversifying to go beyond selling fish and plants as a means to secure their incomes.
Looking at aquaponics rather than IMTA, there’s an indication that, like for all businesses there are multiple factors affecting profitability of an aquaponic business – scale of operations, business acumen of the business owners, local climate, consumer markets, distance to markets etc all having a significant effect.
Community Supported Agriculture (CSA) changes the shape of a business – in agriculture in general, the CSA model has been used to enable small farms to make the most of their sustainability advantages. Things like being close to their consumers, being visible, being able to absorb urban waste streams such as heat and food waste. However using CSA for aquaponics has yet to be studied and is where this Bristol Fish Project comes into the picture. Through setting up an urban community-supported aquaponic farm, and attempting to get it economically viable, we can share our successes and the barriers we encounter, and hopefully develop some kind of framework for community supported aquaponics.