The polyculture of benthic and pelagic aquatic animals can enhance sustainability and profitability in aquaculture. For this to be possible, adverse intraspecific interactions must be minimised. In this two-part study, hybrid lemon fin barb (Barbonymus gonionotus ♀ × Hypsibarbus wetmorei ♂) (HLFB) and red claw crayfish, Cherax quadricarinatus were monocultured or polycultured at increasing crayfish densities in an intensive recirculating aquaculture system (RAS) without physical separation (Trial 1) or with separation (Trial 2). In both trials, the two controls were the monoculture of HLFB (C1) and crayfish (C2). The ratios of fish: crayfish were T1 (75:25), T2 (50:50) and T3 (25:75) for trial 1; while T1 (75:25), T2 (75:50) and T3 (75:75) for trial 2, respectively. After 12 weeks, growth, feeding efficiency, and total production of the HLFB and crayfish were measured. In Trial 1, HLFB growth and feeding efficiency were significantly improved with polyculture, but crayfish survival, growth and feeding efficiency significantly worsened when polyculture. Economic analysis revealed the monoculture of crayfish was more profitable in Trial 1, with a loss of profit in T2 and T3 . In Trial 2, crayfish survival significantly declined in T3 versus T2, but no significant differences in growth or feeding efficiencies of either species were found across treatments. Economic analysis showed that crayfish monoculture was still the most profitable in net return. Still, the benefit-cost ratio was the highest and similar for HLFB across all treatments. Polyculture can spread risk compared with monoculture, but a physical separator is necessary to eliminate intraspecific competition.