Effects of Different Planting Distances on the Growth and Survival of Halymenia durvillei Cultured in a Controlled Medium

The cultivation of seaweeds under controlled conditions represents an important alternative for achieving stable and high-quality production. Halymenia durvillei is a red seaweed species with considerable potential for cultivation using controlled media. This study aimed to evaluate the effects of different planting distances on the growth performance and survival rate of H. durvillei cultured under controlled conditions. The experiment was conducted from May to July 2025 at the National Research and Innovation Agency (BRIN), Pemenang District, North Lombok Regency, West Nusa Tenggara, Indonesia. An experimental approach was employed using a Completely Randomized Design (CRD) consisting of four planting-distance treatments with three replicates: 30 cm (P1), 25 cm (P2), 20 cm (P3), and 15 cm (P4). The parameters observed included absolute weight gain, specific growth rate, survival rate, thallus length, number of thalli, and water quality. Seedlings with an initial weight of 5 g were cultured for 30 days. The collected data were analyzed using analysis of variance (ANOVA), followed by Duncan’s multiple range test using SPSS software. The results indicated that planting distance significantly affected absolute weight gain and specific growth rate, but had no significant effect on the survival rate of H. durvillei. Planting distances of 30 cm (P1) and 25 cm (P2) produced comparably favorable outcomes, yielding absolute weight gains of 5.20 g and 5.49 g, respectively, and specific growth rates of 2.32% day (P1) and 2.47% day (P2). In both treatments, thallus length reached approximately 1 cm, supported by an average thallus number ranging from 32 to 70. Throughout the cultivation period, water quality parameters remained within optimal ranges across all treatments, with temperatures of 25–26°C, pH values of 7.87–8.13, and salinity levels of 30–31 ppt.