Even as humans continue to alter the natural systems that sustain us at an alarming rate, we are becoming aware of cultural practices and technologies that are useful for mitigating and re-mediating our impacts. New techniques are rapidly becoming viable alternatives to existing standards due to the innovation and diligence of individuals and businesses such as Coastview Aquaponics, who follow a calling. For new technologies to be adopted, they must satisfy a few key criteria: Can the new technology be integrated or retrofitted into existing applications? Will the new application be competitive in a reasonable scale of operation? Does the new technology really solve the problem or does it create a new set of issues with long term implications? Instead of following the paradigm of progressively intricate reactions to fundamental problems, some systems operate with such inherent elegance and simplicity that they break the cycle of linear action/reaction that has characterized the “Green Revolution” of the last century.
Two driving questions behind development of sustainable farming technologies are “where do the resource inputs come from?”and “where will the wastes end up?”. The aquaponics approach is an evolution of aquaculture and hydroponic gardening techniques, and has been driven by the goal of creating a closed loop that addresses both of these questions using living organisms in harmony. While worldwide aquaculture practices have raised questions about feed procurement and waste management, and hydroponic systems are heavily reliant on synthetic fertilizers, aquaponic practices minimize these key concerns and operate with ecological efficiency.
Chris and Alexis Smith, proprietors of Coastview Aquaponics, have been in business since January 2010. They provide the Kaloko and north Kona communities with fresh produce that has an impressively small footprint for production and they are actively involved with spreading the use of home-based aquaponic systems. Chris considers farming with aquaponics to be an “assisted ecosystem”, giving credit for the bounty produced to an orchestration of fundamental organisms that manage the waste/nutrient flow and facilitate the all important nitrogen cycle.
The nutrient flow begins with tilapia. Tilapia are an extremely versatile candidate for aquaponic systems due to tolerance of a wide range of dissolved oxygen, temperature, salinity and dissolved solid conditions. In order to maintain the efficiency of his system, Chris works to keep a low ratio of individual fish to plant growing surface area because larger fish metabolize feed more efficiently than a corresponding biomass of small fish. Chris feeds the tilapia a pelletized food for the sake of simplicity and economics. Roughly 10% of the fish diet is augmented by crop residues. This figure was once higher but the Smiths now keep chickens, and have elected to recycle the majority of their crop residues for egg production. The tilapia are kept in a ferrocement rearing tank separate from the plants to prevent them from grazing on the roots, although Chris does use the tilapia to trim the roots of produce in preparation for market packaging.
Ammonia is a waste by-product of the fish and is released through their gills during metabolism or expelled as effluent. The water of the system is populated with two primary species of bacteria which process the phytotoxic ammonia into plant available nitrate. First, nitrosomonas bacteria convert the ammonia into nitrite. Nitrobacter bacteria then convert the nitrite into nitrate. Nitrification is happening in the fish tanks as well as in the plant tubs and growth media and is optimized by the presence of adequate dissolved oxygen provided by aeration and turbulent flow within the system. The ratio of the three nitrogenous species is in constant flux but is inherently stable in a recirculating environment, allowing the plants constant access to nitrogen in a beneficial form. Nutrient enriched water is pumped from the rearing tank to the plant tubs. Nitrification and the carbonic acid cycle both acidify the water of the system slightly, which Chris counteracts with the addition of locally available seashells. The seashells are physically stable and do not dissolve into the water until needed. Plants remove the fish waste products and physically filter solids out of the water before it is pumped back to the rearing tank in circulation. In this system, plants, fish and nitrifying bacteria are all benefiting from the biological processes of each other.
Chris uses a floating raft system in the plant tubs to manage the movement of plants. Seedlings start at the distant end of each greenhouse and are cycled towards the entrance as mature plants are harvested. This system is ideally suited to the nature of the Coastview approach to the local community and customers. Every Saturday Chris and Alexis welcome the public to their farm for free tours and direct sales. Customers are encouraged to select their own produce which is then harvested and prepared by the Smiths. Since the system is inherently clean and soil free, produce is packaged with a mass of roots attached, allowing it to last up to three weeks or more in refrigeration without rapidly losing quality. Coastview occasionally makes sales to retail markets in times of abundance, but prefers to focus more on the immediate local market. In Hawaii, the relevance of this approach cannot be overemphasized, as the vast majority of all food and other goods are shipped in from thousands of miles away.
Another area where Chris and Alexis are taking positive steps forward is public education. Chris offers classes on the principles and construction of small farm and hobby scale aquaponics. He is currently focusing on the advancement of cheaply obtainable, very low footprint home systems, which he sees as an elegant addition to the food security of any family. Since the systems are essentially turnkey, they allow a family or individual to become familiar with aquaponics without feeling intimidated by the details of operation. A small pump to circulate water and an aerator are wired through a timer within an economical waterproof housing, and the system uses around 30 cents of electricity daily. The small systems are very user friendly- bubbling water and vertical cascades of plants lend appeal of the senses to an inherently stable ecosystem. Species of fish can be selected that anticipate feeding time and come to the surface to interact, creating a wonderful opportunity for children of all ages to be part of growing food.
In order for a concept like aquaponics to take root in food production practice, it must be efficient, elegant, and produce a high quality food. Operations like Coastview Aquaponics are doing the footwork necessary to work out the details of operation and marketing strategies that will forward the use of aquaponics in the future. Aquaponics technology is viable in scales of operation anywhere from patio systems to thousands of acres of fertigated crops. To watch fish swirling in the watery shadows and then observe the vibrant plant growth that is facilitated by symbiotic existence is an ethereal sensation, and a wonderful introduction to animal husbandry for people of any background. Aquaponic systems are economically and ecologically sound, and will continue to be a valuable tool in the development of a sustainable future.
Essay by Herbert Kruger
Sources and Links:
Personal interview by author of Chris and Alexis Smith,
ATTRA Aquaponics Primer
National Sustainable Agriculture PDF publication with excellent links.
Community forum designed to support the flow of ideas in this emergent field.
Urban Aquaponics Manual
Comprehensive design/operation database available by subscription.