Location: Aquatic Animal Health Research
2025 Annual Report
Objectives
1. Develop, evaluate, and improve fish production systems for aquaponics.
Component 6: Problem Statement 6A
2. Develop, evaluate, and improve plant production systems for aquaponics.
Component 6: Problem Statement 6B
3. Develope environmentally and economically sustainable aquaponic systems.
Component 6: Problem Statement 6C
Approach
Auburn University faculty and their associated research team and ARS investigators will work collaboratively on both the aquatic animal and plant components in an effort to improve the yield and efficiencies of aquaponics production systems. Topics of interest to be explored include the optimization of: aquaculture system type, fish feeds, stocking densities, alternative aquatic species (e.g., high-value species such as pompano, red drum, cobia, marine shrimp, etc.), oxygenation strategies, animal and plant disease management, plant yields, improving nutrient and water use efficiencies, postharvest product quality, and salt tolerance.
Progress Report
This is the final report for project 6010-32000-028-000D, Improving Aquaponic Systems to Produce Fish and Plant Products, which has been replaced by new project 6010-10600-000-001D, Optimizing Aquaponic Production Systems for Production Efficiency and Profitability. For additional information, see the new project report.
In a recent investigation, a biofloc system was combined with a deep-water hydroponic plant system to determine the effects of fermented yeast products on the growth and health of fish and plants.
Research continued to determine why tomato plants wilt when excess sludge accumulates in a media grow bed. Under moderate sludge loadings, there is no negative effect on plants and sludge is an important reservoir of nutrients, such as iron and calcium. It also hosts many beneficial bacteria. However, when sludge levels accumulate in excess, water drainage declines, and it was shown that wilting plants had significantly lower dissolved oxygen in their root zones than healthy plants within the same grow bed. Such plants also had higher abundances of parasitic nematodes based on sequencing results. In new trials, a clarifier was added, in addition to a filter, to remove sludge that flows from the fish tank into the plant bed. Although this reduced the amount of sludge from the fish tank, large volumes of sludge still accumulated in the grow bed. This highlights the need to make sure the plant grow system is large enough to accommodate the nutrient input from the fish system. Doing so can extend the tomato growing season and ensure healthier plants.
Researchers at the ARS Auburn, Alabama lab have planned, designed, and constructed a 2000-L freshwater, coupled, multi-tiered aquaponic demonstration system in which red swamp crayfish serve as the organismic nutrient source for a variety of vegetables and spice plants. Currently, three different kinds of peppers are being grown in the system (bell, banana, and cayenne) as well as sea purslane. Concurrently with the design and construction of the freshwater aquaponic system, a 2000-L coupled brackish-water (11 ppt) aquaponic system has been constructed and operating to grow halophytes and marine shrimp (whiteleg shrimp). The halophyte presently being grown is sea purslane; however, sea asparagus propagation and cultivation efforts are being planned and will also be grown in the system. Additionally, ARS researchers (Auburn, AL) designed and constructed an outdoor, 4000-L coupled, freshwater aquaponic system with two 3-m plant trays which are growing snap dragons, bell peppers, banana peppers, and cayenne peppers. Nile tilapia juveniles are being grown in the fish component of the system.
Accomplishments
1. Product quality was unaffected by an aquaponic system coupling and fish tank light penetration. A study was conducted at Auburn University using 4 different designs to evaluate (a) systems coupling (versus decoupling), and (b) allowing sunlight to penetrate the fish tank versus a dark tank. These treatments led to significantly different microbial community structures and different yields of fish and plants. A coupled aquaponic system significantly increased yields for both fish and plants; however, no differences in quality of fish or tomatoes were detected by an untrained taste panel. Off flavor molecules in fish (MIB and geosmin) were generally low in all systems with only two individual systems showing levels above the human detectable threshold. For tomatoes, sugar content, brix, and total acidity generally did not respond to treatment: variation over time was the most important factor. The latter may be a reflection of the changing light and temperature levels across the different seasons of production. These results indicate that product quality (fish and tomato) was unaffected by the aquaponic system used.
2. Algae-based aquaponic system improves tomato yield while novice aquaponic operators can be successful. Over 23 million American households reside in food deserts, predominantly affecting communities in urban areas. Aquaponics holds promise to allow local residents to cultivate fresh fish and vegetables. However, limited technical knowledge, system instability, and poor product quality pose barriers for novice users. A study was conducted at Auburn University investigated how design choices influence system stability, user-friendliness, and product quality. Expert researchers managed three replicates, while novice users operated four additional replicates. In the study, most systems maintained stable nitrification with minimal ammonia levels. However, when fish were introduced, decoupled systems experienced a brief ammonia spike due to increased organic load and insufficient nitrifier abundance. In contrast, coupled systems benefited from the higher organic load, boosting nitrification and nitrate levels, while decoupled systems saw a decrease in nitrate levels due to the dilution effect. Algae-coupled systems outperformed bacteria-coupled systems in terms of achieving the highest fish growth. Furthermore, despite lower nitrate levels in algae-coupled systems compared to bacteria-only coupled systems, they obtained superior tomato biomass production. This may suggest that in algae- coupled systems, plants were able to absorb nitrate efficiently even though a lower amount of nitrate was available. Results indicate that novice users can successfully operate aquaponic systems and that algae-based coupled systems may be preferred for growing tomatoes.
3. Addition of enzymes (proteases) and acids altered microbial communities, but did not increase growth in Nile tilapia or lettuce in a biofloc aquaponic system. Aquaponics and biofloc-based aquaculture systems are environmentally sustainable food production systems. When biofloc technology is combined with hydroponic systems, it expands economic diversity by producing additional value-added products. Dietary additives were incorporated into fish feeds in this trial to improve food production in a decoupled aquaponic systems. In this decoupled aquaponic system, the biofloc aquaculture system consisted of nine cylindrical tanks with Nile tilapia stocked in each tank. The fish were randomly assigned to one of three treatment groups: fish fed a commercial feed, commercial diet + protease complex, and commercial feed + humic substance. The feeding trial was conducted for 60 days, and the plants (Romaine lettuce) were grown in floating rafts. Fish and plant growth parameters showed no differences between treatments; however, the leaf greenness in romaine lettuce plants in the diet containing protease complex treatment had significantly higher chlorophyll content than the other treatments. When microbial communities were analyzed, significant differences were found among the different dietary treatments in water, fish feces, and lettuce roots. Overall, this study concluded that these additives did not affect the growth of Nile tilapia and romaine lettuce, but did influence the bacterial composition of fish feces, water, and root samples, and the chlorophyll content of the plants.