Aquaculture Nutrition. 2018;1–8. wileyonlinelibrary.com/journal/anu | 1 © 2018 John Wiley & Sons Ltd 1 | INTRODUCTION Due to growing interest in aquarium keeping, ornamental fish indus- try is receiving increasing attention these days. Successful ornamen- tal fish trade depends on producing animals of good size and bright colours, the latter being directly linked to the commercial value (Simpson, Katayama, & Chichester, 1981). Electric yellow cichlid (Labidochromis caeruleus) is a freshwater species from the family Cichlidae. Members of this family are extremely popular as aquar- ium fish. The skin pigmentation derives from carotenoids deposited in tissue (Simpson et al., 1981). Aquarium fish fail to maintain the skin coloration as a result of carotenoid deprivation, which negatively af- fects consumer acceptance. Fish cannot synthesize carotenoids de novo (Goodwin, 1984) and must acquire them directly from dietary Received: 19 July 2018 | Revised: 7 November 2018 | Accepted: 8 November 2018 DOI: 10.1111/anu.12869 ORIGINAL ARTICLE The effect of supplementing diets with extracts derived from three different species of macroalgae on growth, thermal stress resistance, antioxidant enzyme activities and skin colour of electric yellow cichlid (Labidochromis caeruleus ) Faezeh Pezeshk 1 | Sedigheh Babaei 2 | Abdolmohammad Abedian Kenari 3 | Mehdi Hedayati 4 | Mahmood Naseri 2 1 Department of Fisheries, Faculty of Agriculture, Khazar Institute of Higher Education, Mahmood Abad, Mazandaran, Iran 2 Department of Natural Resources and Environmental Engineering, School of Agriculture, Shiraz University, Shiraz, Fars, Iran 3 Department of Aquaculture, Faculty of Marine Sciences, Tarbiat Modares University, Noor, Iran 4 Cellular and Molecular Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran Correspondence Sedigheh Babaei, Department of Natural Resources and Environmental Engineering, School of Agriculture, Shiraz University, Shiraz, Fars, Iran. Emails: Babaei.Sedigheh@gmail.com; s-babaei@shirazu.ac.ir Funding information Khazar Institute of Higher Education Abstract The purpose of this study was to evaluate the growth, thermal stress resistance, an- tioxidant enzyme activities and skin colour of Labidochromis caeruleus (electric yellow cichlid) fed the diets supplemented with extracts derived from brown macroalga Sargassum boveanum, red macroalga Gracilaria persica and green macroalga Entromorpha intestinalis. One hundred and forty-four fish were randomly distributed into 12 tanks and subjected to cold-shock stress after 8 weeks of feeding the diets containing 1,000 mg extracts of macroalgae. Supplementation of fish diet with algal extracts led to improved growth performance (including higher final weight and weight gain) when compared to the control group, which was fed the non-supple- mented diet. The survival rate after cold-shock stress was significantly higher in those fish fed the diets containing macroalgal extracts, especially E. intestinalis ex- tract (75%). The superoxide dismutase activity in all dietary treatments was signifi- cantly lower than control, whereas no significant difference in the activities of catalase and lysozyme was observed among treatments. In addition, inclusion of macroalgal extracts in the diet resulted in higher a* (redness) and b* (yellowness) values compared to the control group. These results suggest that macroalgal ex- tracts, especially E. intestinalis extract, can be used as feed additive for increasing antioxidants capacities as well as enhancing pigmentation in electric yellow cichlid. KEYWORDS antioxidant defence, cold-shock stress, fish skin pigmentation, growth performance, Labidochromis caeruleus, macroalgal extract