The sea cucumber Holothuria scabra, or sandfish, is a commercially valuable aquaculture
species; however viable intensive tank-based aquaculture techniques have not yet been
developed. The study aimed to assess the role of sand as a substrate and/or dietary component
in intensive tank culture of sandfish in recirculating aquaculture systems (RAS) in South
Africa. A control experiment was conducted to confirm the reported positive effect of sand as
a substrate on sandfish growth and a sand-in-diet experiment was conducted to determine if
incorporation of sand into formulated diets could improve sandfish growth in bare tanks. In
the control experiment, mean growth rate of juvenile sandfish in the bare tanks was
significantly lower than that of juveniles reared in tanks with a sand substrate (-0.12 ± 0.16 g
day-1 SE and 0.03 ± 0.01 g day-1 respectively; F (1,2) =1.91, p < 0.001). However in the
sand-in-diet experiment, mean growth rate of juvenile sandfish in bare tanks, fed a
formulated diet containing 20 % sand was not significantly different to juveniles fed a
standard formulated diet (-0.13 ± 0.01 and -0.12 ± 0.16 g day-1 respectively; F (1,2) =1.26, p
> 0.05). Results confirmed the reported positive effect on sandfish growth when sand is
provided as a substrate, however sand in diets did not promote growth in the same way,
indicating that inclusion of sand in formulated diets is unlikely to compensate for lack of sand
as a substrate. Future research should therefore aim to identify optimum parameters of sand
substrate and develop tank holding systems capable of maintaining favourable substrate
conditions for intensive sandfish culture.