The Effect of Red Wiggler Worms (Eisenia fetida) on Aquaponics
Nutrient Solution Properties and System Stability Across Solution Temperature
Andrew Haberman (Masters Candidate, Professional Studies in Horticulture), Mitchal Peterson (Bachelor of Science Candidate, Department of Horticulture), and Allison Ruby (Bachelor of Fine Art Candidate,
Department of Art, Horticulture Minor.)∗, University of Minnesota-Twin Cities. Faculty Advisor: Dr. John Erwin*Equal contribution by all authors.
Overview
This project begins to quantify the potential benefit of red wiggler worms as a low cost input for aquaponics producers to increase nutrient concentration available to plants and thus increase
subsequent yield. Through regular testing and analysis of the system’s nutrient solution, it was found that worms had no immediate, consistent, and demonstrable benefit as far nutrient
concentration, system stability, or plant yield, and that fish species had more of an effect on system solution. This study does not rule out other benefits of worms to the system, in particular to the
reduction of waste build up. Inconclusive results suggest that this study should continue over a longer duration.
Methods
Findings
• Red wiggler worms (Eisenia fetida) were added to the biofilters of four of
eight floating raft aquaponics systems.
• Tanks contained Nile tilapia (Oreochromis niloticus) or yellow perch
(Perca flavescens), and were maintained at either 23°C or 26°C.
• Plant crops for all systems were butterhead lettuce (Lactuca sativa 'Nancy'
OG MTO) and purple basil (Ocimum basilicum 'Amethyst Improved').
• Over six weeks tracked major and micronutrient,
pH, and alkalinity levels in the four systems with
worms, as well as four identical systems without
worms. Plant yield was also measured.
• Evaluated whether there were measurable differences in
nutrient solution composition between the systems with or
without worms. Also looked for synergistic differences between
worms and other variables of fish species and temperature.
Summary of Treatments
Tilapia
23°C
Perch
Worms
Tilapia
26°C
Perch
Tilapia
23°C
Perch
No Worms
Tilapia
26°C
Perch
Nutrients Measured: NO3
NH4
P
Ca
Mg
Na
Fe
3
600
2.5
2.5
2
2
400
300
200
Fe in ppm
3
500
1.5
1
0.5
0
0
0
4
5
6
Tank Number
Orange bars: Tanks with worms.
7
8
1
2
3
4
5
6
7
8
Tank Number
Blue Bars: Tanks without worms.
1: Add Red Wiggler Worms to Aquaponic Systems
Although the data did not support the nutrient based beneficial effects of red
wiggler worms, they are very inexpensive, and well known for their ability to
reduce waste build up in aquaponic systems (Rakocy et al., 2006. Aquaponic
growers can benefit from decreased expenses associated with system cleaning.
2: Extend Duration of Research with Improved Protocol
Limiting these variables and extending the duration of the experiment will
provide better information on the potential long term benefits of worms.
1
0.5
3
Recommendations
Mo
1.5
100
2
Cu
Average Fe in ppm
700
1
Mn Zn
Average K in ppm
K in ppm
ppm NO3
Average NO3 ppm
K
Dark shades: Tanks with Perch.
1
2
3
4
5
• There was no statistically relevant data to support the hypothesis that the inclusion of red
wiggler worms in an aquaponic system’s biofilter increases nutrient concentration.
• There was a significantly greater output of nitrate and soluble salts in the tanks that
contained tilapia than those with perch.
• Iron and zinc levels were higher in the aquaponic systems with worms
added to the biofilter.
• The potassium concentration in the aquaponic systems with worms added
to the biofilter was lower than that of the systems without the addition of
worms..
• In a study measuring nutrient outputs, one must pay close attention to
limiting factors that affect the systems composition. Having different types
of fish, different crops, and different water temperatures all greatly affected the accuracy of
whether or not worms had an effect on the nutrient concentration of the systems.
6
7
8
Tank Number
Light shades :Tanks with Tilapia
Acknowledgements Funding for this research was funded, in part, by the Minnesota Agricultural Experiment Station and a grant from the College of Food, Agricultural and
Natural Resource Sciences Program for Creation of New or Revised Courses and Programs for Experiential and Interdisciplinary Education, entitled “Aquaponics: To fish
and plant…for life! We would also like to acknowledge the Research Analytical Laboratory at the University of Minnesota for providing nutrient solution analyses.
Citations: Rakocy, J. E., Masser, M. P., & Losordo, T. M. (2006). Recirculating aquaculture tank production systems: Aquaponics- integrating fish and plant culture. Srac
Publication - Southern Regional Aquaculture Center, 1–16. doi:454