Aaron Cardona set out to grow tilapia and traditional Mexican greens in a greenhouse using an integrated aquaponics system powered by solar energy in the Chihuahuan Desert of Southeastern Arizona. In a rural area of very conservative and traditional farming, the project looked to test the viability of aquaponics in the area, introduce a fresh water fish in the desert, and provide two water heavy crops, berros (watercress) and verdolagas (purslane), traditionally eaten by the Hispanic population of the area. It also looked to build a more economically viable system that could be replicated by the local low-income population of the area or by those looking to utilize space efficiently in their greenhouse while utilizing renewable energy to fuel the system.
There were five objectives for the project:
*explore the viability of aquaponics in the Desert Southwest;
*increase the availability of traditional foods locally;
*construct a more economically viable aquaponics system;
*make a greenhouse operation truly sustainable by using solar energy;
*serve as an example of sustainable agriculture for the local agriculture community.
During the initial research stage, it was determined that greenhouse would exceed the optimal 65-80 degree temperature for the tilapia, so a cooling system was installed to maintain the temperature for the greenhouse during the harsh summer months.
Research was performed to locate an aquaponics expert in the area to design and construct a cost-efficient system that could be easily replicated by anyone. Once the expert was contracted, a design was drawn up in accordance with the size and ability of the current greenhouse and the desired tilapia and greens capacity. Another huge decision was to move towards a media based growing bed, composed of lava rock and clay pebbles, as opposed to a rafter system utilized by Nelson and Pade in their pre-manufactured aquaponics systems.
A local source of supplies for aquaponics was located and the construction began on the system. Once the system was constructed, an additional element caused a huge obstacle to the completion; the cold winter of the Chihuahuan Desert. The temperature at night dropped well below the lowest possible temperature that the tilapia could survive of 60 degrees. Without the luxury of an industrial, heated greenhouse, aquarium heaters needed to be purchased for the fish tanks in order to maintain the water at a desirable temperature for the fish to thrive.
Once the issue of heat was resolved, fish were added to the start cycling the system with fish emulsion to create a nutrient rich environment so that the watercress and purslane could be planted. Two weeks later the two greens were planted. The purslane struggled and germinated 10 days later and continued to struggle for its entirety until it ultimately was removed after two months of stagnation. The watercress on the other hand germinated in four days. In a matter of 41 days, the watercress started being harvested and we never looked back.
Tarps were added to the tanks to block the sun and control algae, which take up oxygen in the system. The pH maintained well and ammonia levels have not been an issue. The transition from winter into warmer temperatures started to affect algae levels, rapid water evaporation, and plant health. Shade cloth was pulled which immediately brought the system back to health.
Tilapia was added to the system at two different times and at different growth stages. The first fish added to the system were at medium size, as they were seen as stronger and less susceptible to being affected by the colder temperatures and dying. One fish did perish during the winter, the cause of death is unknown.
The second round of fish was added about six weeks later during warmer weather at fingerling size. These fish doubled their size in two weeks and keep growing. Of the original medium sized fish added to the system first, eight are about 1.5 lbs and ready to eat.
The project has proved to be a success. In the rural area of Cochise County, which is dominated by large industrial agriculture, the aquaponics system has caused a stir in the community. Knowledge of fish grown in a greenhouse has spread far and wide, bringing many to come and ask how to set up their own system. By fulfilling one of the project goals of constructing an aquaponics system for more than half of the cost of a pre-manufactured system, it is now more accessible to a wider range of people of different backgrounds and income.
The economic analysis and potential is something that needs to be highlighted. The availability of watercress locally is of huge consequence. I took great pleasure in the double takes people would make at the farmer’s markets when they saw berros (watercress) for sale. Even more so were the countless stories of people telling me how long it had been since they ate watercress and the stories of gathering it wild in streams, rivers, or ponds. The few areas in the region where it can be harvested during the monsoon are dangerous because of the harmful bacteria, toxins, and such that are accumulated upstream. To be able to produce it in a healthy system year round is a huge economic potential for sale to markets, coops, and restaurants.
It is also worth noting that the reintegration of berros has been successful for attracting more people of Hispanic descent. The percentage of people of Hispanic descent is drastically lower at farmer’s market when compared with those of non-Hispanic descent. However, due to the publicity of the project, I would calculate that nearly 40% of my sales have been to people of Hispanic descent. I deduct that the integration of more culturally appropriate and traditional foods can bridge the gap and increase the participation of the Hispanic population at farmer’s markets.
Educational & Outreach Activities
The project was communicated through a variety of different formats. The complete project was updated periodically via pictures and videos on the Arevalos Farm Facebook page. These updates built up publicity for the three major aquaponics demonstrations that took place at the farm. The first demonstration was given to Double Adobe Elementary School, which included 45 students from grades K-6, as well as teachers and students. The second demonstration brought students from Cochise College to include 50 college freshmen and sophomores. The last demonstration was open to the whole community and was well attended. More than fifty people attended and learned about the entire project, and local aquaponics expert Claudio Rodriguez educated all about the science of aquaponics. Field day surveys were passed out to the Cochise College students and the people who attended the Field Day.
As a result of this, three local newspapers featured a front page article entitled, “The Freedom to Stay Home,” which centered around the newly installed aquaponics system and the innovation Arevalos Farm is pioneering in the area. This brought many out to the farmer’s market to talk to me about the system and to request additional field days at the farm. I used the publicity at the farmer’s market to pass out aquaponics fact sheets and to direct them to the facebook page and my youtube video developed in coordination with Claudio Rodriguez in which he lays out the basics of aquaponics. Also as a result of the newspaper, an invitation was extended by the Cochise County Master Gardeners to present on Aquaponics.
The fact sheet and link to video are attached.
As a traditional soil based farmer, aquaponics has also sparked my interest beyond the economic analysis. In soil based farming, you are always concerned with building up your soil with nutrients, having to weed and then prepping the soil for planting. In aquaponics with a growing medium such as clay pebbles, you are able to create almost perfect soil conditions complete with nutrients, beneficial bacteria, and lots of nitrogen to feed your plants in a matter of weeks. There are no weeds or Bermuda grass or Johnson grass! If you don’t understand then you’re either the luckiest person alive or not an organic grower. You can plant so close together to double your plant population, maximizing your space in a greenhouse, which is high real estate. To have all these headaches resolved and have the tilapia fertilize the plants for me, until they are ready to eat or be sold can only be summarized in one word: Amazing.
As was pointed out, the purslane turned out to be an utter failure. None of the plants developed into anything close to being harvested and thus was pulled from the tank. Watercress on the other hand, proved to be a great success. With its marketability and the failure of purslane, more watercress was sown to take its place and utilize the system to its fullest.
Survey results from demonstrations are attached below.
Fresh water tilapia!?! It’s virtually an unexplored world with colossal potential. Although my fish are barely getting to the point to eat, I have been approached by many at farmers markets asking to buy them and sought out by a popular four-star restaurant salivating over the potential to serve locally grown tilapia.
The aquaponics project was successful in many areas; however, there are still many facets to research. I believe that there needs to be an economic feasibility study on growing tilapia in the region. There also needs to be more research on other possible fish that may possibly be better suited for the climate of the Desert Southwest, especially for those who can not afford to install a renewable energy source. Some have suggested testing the feasibility of shrimp in an aquaponics system. Whatever it may be, more research should be conducted to find an economically viable animal that can match the success of the watercress. Furthermore, I believe that much more effort needs to be done to re-institute more traditional foods back into the region. Perhaps more importantly, a health study needs to accompany this reintegration to give scientific evidence which link the improvement of health and well being with traditional foods.