The Feasibility of a Small-Scale Aquaponics System Utilizing a Partial Mealworm Feed Substitution

Abstract

This study compared fish and plant growth rates when implementing a partial insect meal (IM) substituted feed. Two 12-week greenhouse studies with mealworm beetle (Tenebrio molitor) feed substitutions of 0% (fishmeal control), 15%, and 25%, and Nile tilapia (Oreochrimis niloticus) were used in both trials. Butter lettuce (Lactuca sativa) was grown in the first trial. Ethiopian kale (Brassica carinata), collard greens (Georgia southern), and chickpea (Sierra kabuli) were grown in the second trial. Weekly water quality samples of macro and micronutrients were collected and analyzed. The study also considered capital investment, operating expenses, and revenue to determine economic feasibility based on production. In the first trial, there was no significant difference (p≤0.05) in the total fish biomass gained between the control and 15%IM treatments and between the 15%IM and 25%IM treatments. However, there was a significant difference (p≥0.05) in the total fish biomass gained between the control and 25%IM treatments. In the second trial, there was a significant difference (p≥0.05) between the control and 15%IM, but no significant difference (p≤0.05) between the control and 25%IM or the 15%IM and 25%IM. Hydroponic output varied over both trials as 15%IM produced the highest plant biomass in the first trial and 25%IM produced the most plant biomass in the second trial. Chickpea harvest data for the second trial is unavailable at this time as the chickpea are yet to fruit. Greenhouse operations were deemed to be unprofitable as annual revenue extrapolated from the first trial was only $1,600. Due to the use of smaller fish and the reduction in overall plant biomass in the second trial, annual revenue is expected to decrease. Capital costs for the greenhouse setup and the outdoor alternative were $17,000 and $44,500. Annual operating expenses were $12,700 and $5,400 for the greenhouse and outdoor alternative.