Nutrients recycling efficiency of hydroponic grow-outs in an indigenously designed low-tech aquaponic system

Abstract

A low-cost DIY (do-it-yourself) coldwater aquaponics system was developed to evaluate the performance of three hydroponic grow-out types i.e. river stone (T₁), crushed stone (T₂) and raft/deep water culture (T₃) without a dedicated external biofilter. Rainbow trout (Oncorhynchus mykiss) and lettuce (Lactuca sativa) were co-cultured for 45 days, with a fish-only unit as control. Crushed stone (149.11±0.532) and river stone (148.34±0.467) treatments registered significantly higher final weight of rainbow trout than other experimental groups while significantly higher final weight of lettuce were recorded in all treatments than control (89.15±4.37). Water quality regulation and nutrient recycling efficiency served as performance indicators. Gravel-based and raft systems effectively stabilized water parameters compared to the control. Nitrite (78.874±2.331%) and total dissolved solids (0.794±0.018%) removal were highest in river stone and raft systems respectively, while crushed stone achieved maximum stripping off of vital nutrients like total ammonia nitrogen (86.166±0.221%), nitrate (71.677±0.203%) and phosphate (61.869±0.943%). Considering the studied criteria, the stone substrate-based aquaponics can be suggested for small scale farming in low thermal agro-climatic regions.