Optimizing coral reef fish larviculture: Significance of iron addition to inorganic fertilization method

Historically, attempts to cultivate marine ornamental fish larvae have been mostly unsuccessful, primarily due to insufficient live feed to meet the diverse requirements of different fish species. This study examined the effects of iron supplementation on the survival of coral reef fish larvae using the inorganic fertilization method. Experiments were conducted in 2000 L tanks, each stocked with 5000 eggs from a mixed population of over 10 coral reef fish species. The design included two treatments: a control group and a +Fe group supplemented with 10 μg L⁻¹ iron. Water temperature ranged from 27 to 29℃, with stable salinity (∼32 psu), pH (8.2–8.4), and dissolved oxygen levels (>7.4 mg L⁻¹) across treatments. Iron supplementation increased > 20 μm phytoplankton abundance in Exp. I and supported zooplankton densities exceeding 20 × 10 ³ ind L⁻¹ . Plankton diversity was high, with over 16 taxa detected in water samples and more than 11 taxa in larval stomach contents, including Dinoflagellata, Ciliophora, Arthropoda, and phytoplankton groups (Chlorophyta, Bacillariophyceae, Rhodophyta, and Haptophyta). Larval survival significantly improved with iron addition. In Exp. I, survival was 16 ± 14 % in the +Fe group versus 7 ± 4 % in the control (p > 0.05), while Exp. II showed a significant increase from 9 ± 7 % (control) to 26 ± 11 % (+Fe) (p < 0.05). Species diversity among survivors was also higher in the +Fe group. Overall, supplementing 10 μg L⁻¹ iron alongside inorganic fertilization (N: 700 μg L⁻¹, P: 100 μg L⁻¹) enhances larval survival, offering a promising strategy for coral reef fish larviculture. • We raised larval fish using inorganic fertilization method, w/without Fe addition. • Fish stomach consisted > 10 species of plankton. • Larval fish survival rate was significantly higher when Fe was added. • This can be an alternative way in coral reef fish larviculture worldwide.