Can bacterial biofiltration be replaced by autotrophic organisms in recirculating fresh water aquaculture?

Suvi Ojanen, Esa Tyystjärvi*, Henrik Holmberg, Mikko Kouhia, Pekka Ahtila

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review


In recirculating aquaculture, a bacterial biofilter is applied to convert ammonium, excreted by the fish, to the non-toxic nitrate. Unfortunately, nitrifying bacteria produce off-flavor compounds that lower fish quality. We investigated, by calculations and estimations, possibilities to replace the biofilter by autotrophic organisms that incorporate ammonium in biomass, consume other mineral nutrients and produce marketable biomass and oxygen. The capacity of microalgae, macroalgae, duckweed, strawberry, and tomato to assimilate ammonium was calculated, using data from an existing Finnish fresh water fish farm. Microalgae were found to be the most effective for ammonium removal, and they would be able to consume the ammonium produced by a fish farm if the algae were grown in a facility with approximately twice the area of the fish farm itself. Macroalgae and duckweed appeared to be the second best option for ammonium removal, and strawberry and tomato were predicted to have a somewhat smaller capacity for ammonium removal. Due to low ammonium content, microalgae cannot be cultivated in the recirculating water, but rather the nutrients should be allowed to diffuse through a semipermeable membrane to microalgae.

Original languageEnglish
Pages (from-to)1427-1440
Number of pages14
Issue number4
Early online date18 Feb 2017
Publication statusPublished - Aug 2017
MoE publication typeA1 Journal article-refereed


  • Ammonium
  • Bacterial biofiltration
  • Macroalgae
  • Microalgae
  • RAS
  • Recirculating aquaculture


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