Application of a Modified Booster System in the Polyculture of the Swamp Eel (Monopterus albus) and the Nile Tilapia (Oreochromis niloticus) in Brackish Water

Abstract

This study aimed to evaluate the optimal stocking ratio and the effects of a modified booster system with recirculation on growth performance, survival rate, physiological response, and water quality in the polyculture of Asian swamp eel (Monopterus albus) and saline tilapia (Oreochromis niloticus) cultured in brackish water (10 ppt). The experiment was conducted for 56 days, from July to September 2025, using a completely randomized design with seven treatments: P1 (eel monoculture), P2 (tilapia monoculture), P3 (1:1), P4 (1:1.5), P5 (1.5:1), P6 (1:2), and P7 (2:1), each with three replications. The booster system was equipped with mechanical and biological filtration units (biofoam, zeolite, and bioball) and supported by the application of probiotic boosters in the rearing medium, feed, and fish immunostimulants. The results showed that different stocking ratios significantly affected the growth and survival of both species (P<0.05). Treatment P3 (1:1 ratio) yielded the highest weight and length growth in both eel and tilapia, with specific growth rates of 2.15%/day and 2.57%/day, respectively. The highest feed efficiency was also observed in P3, reaching 46.22% for eel and 52.56% for tilapia, with the lowest feed conversion ratios (1.41 and 1.90). Survival rates reached 83.33% for eel and 90% for tilapia, indicating that a balanced species ratio created a stable environment that reduced stress and improved energy utilization. Hematological analysis showed the best physiological condition in P2 and P3, whereas elevated leukocyte and glucose levels in high-density treatments (P6 and P7) indicated stress responses. Water quality parameters during the experiment remained within the optimal range for both eel and saline tilapia.