Significant factors affecting the economic sustainability of closed backyard aquaponics systems. Part IV: Autumn herbs and polyponics

Ulrich Knaus, Samuel Appelbaum, Harry W. Palm

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

Two identical coupled ebb-and-flow gravel substrate aquaponics units (each 3.81 m3 – domestic backyard) were tested for extensive fish and herb productivity under autumn conditions in northern Germany (Mecklenburg-Western Pomerania). Common carp (Cyprinus carpio) were stocked in unit I with 10,033.3±305.5 g (number 226, initial weight 35.0±18.1 g) and Nile tilapia (Oreochromis niloticus) in unit II with 10,333.3±757.2 g (number 309, initial weight 26.5±9.9 g) initial biomass and a daily feed input of 200 g or 52.5 g m-3 of system water volume (19.9 g feed per kg fish day-1 and 2.0% feed for C. carpio; 19.4 g feed per kg fish day-1 and 1.9% feed for O. niloticus). Fish growth parameters were higher in O. niloticus (final biomass 19,450.0±50.0 g, SGR 0.91±0.10% d-1, FCR 1.54±0.14) than in C. carpio (final biomass 18,000.0±50.0 g, SGR 0.84±0.05% d-1, FCR 1.76±0.07). Mint yield (Mentha piperita) was 1.8 times higher (20.7±18.0 g) in the O. niloticus unit (II), and basil (Ocimum basilicum) yield was slightly higher in combination with C. carpio (22.1±17.5 g) than with O. niloticus (16.1±13.8 g). Parsley production (Petroselinum crispum) was below expectations, but yield was 2.4 times higher combined with C. carpio (1.2±1.1 g) than with O. niloticus (0.5±0.5 g). The different fish species affected the aquaponics system’s stability with higher dissolved oxygen levels, a longer steady state phase and higher nitrate levels in the C. carpio unit. This experiment demonstrates a different influence of C. carpio and O. niloticus on plant growth expressed by the Aquaponic Growth Factor (AGF), which was higher for O. niloticus only with mint (0.84) in contrast to C. carpio with basil (0.37) and parsley (1.44). The combined use of different fish species in one coupled aquaponics system can compensate for lower growth rates of fish (C. carpio) with a better plant growth of basil and parsley with regard to economical gross output. This form of aquaponics production combines polyculture with aquaponics (POLYPONICs) and can increase the overall yield of the system for sustainable production in aquaponics.

Original languageEnglish
Pages (from-to)1760-1775
Number of pages16
JournalAACL Bioflux
Volume11
Issue number6
StatePublished - 30 Dec 2018

Keywords

  • Aquaponic Growth Factor
  • Aquaponics
  • Carp
  • Ebb-and-flow
  • Fish and plant combination
  • Polyponics
  • Tilapia

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