Co-cultured of red hybrid tilapia and Gracilaria changii (Gracilariaceae: Rhodophyta): Effects on water quality, growth performance and algal density

ABSTRACT

We evaluated the potential for co-cultured of red hybrid tilapia with Gracilaria changii in two different densities in zero water exchange conditions. Five treatments were performed, consisting of three monoculture systems as controls: algae at two different densities (M1 and M2 with 1 g L⁻¹ density and 3 g L⁻¹ density, respectively) and fish without algae (Mfish). For comparison purposes, the other two treatments were co-cultured fish with algae at densities of 1 g L⁻¹ (P1) and 3 g L⁻¹ (P2). The effects of different culture systems and densities on the water quality, growth performance, nutrient content and C/N ratio of the algae were determined. During the experimental period, the dissolved oxygen (DO) and pH values in the algal tanks (monoculture and co-culture) were significantly higher than those in the Mfish tank. The ammonia and nitrate concentrations in P1 and P2 were significantly lower compared to initial measurements. The water parameters indicated that the algae improved the water quality of the culture system. Compared to the fish monoculture (Mfish), the fish grew better with algae (P1 and P2) maybe due to the more favourable water conditions in the tanks. On day 20, the algae growth rates in the co-culture tanks (P1 and P2) were significantly higher than those in the monoculture tanks. Additionally, P1 and P2 improved the nutrient composition and C/N ratio of the algae. This study found that although the co-culture system resulted in better water quality and nutrient content in the alga, the algal density had no significant effect on fish or algal growth.

KEYWORDS:

• Algal biomass
• Freshwater fish
• Nutrient content
• Polyculture
• Red algae

ACKNOWLEDGEMENTS

We thank Mr Hanan Mohd Yusof and his team at Freshwater Fisheries Research Institute, Glami Lemi, Jelebu, Malaysia, for their technical assistance. We also extend our appreciation to the Institute of Biological Sciences for providing the necessary laboratory facilities for this research.

DISCLOSURE STATEMENT

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00318884.2024.2336876

Additional information

Funding

This research has been sponsored by the Ministry of Higher Education Malaysia through the Fundamental Research Grant Scheme (FRGS/1/2019/WAB01/UM/02/3) awarded to Dr Norhidayah Mohd Taufek.