Table 1: ARID pond and conventional raceway characteristics.

Conventional RacewaysARID Pond

Volume780 L (each)7500 L
Surface area3 m250 m2
Surface area: volume ratio1 : 2601 : 150
Culture depth25.4 cmBasin 1: up to 15 cm
Basin 2: 20 cm
Canal (day): 60 cm
Canal (night): 150 cm
MixingPaddle wheel rotating at 6 rpmGravity driven flow from top basin to canal. Aeration at night
Current velocity0.25 m s−10.003 m s−1
Reynolds number*26906407
EvaporationCorrected daily before samplingCorrected every 2-3 days to maintain salinity at 35 ppt
Temperature managementCovered at dusk, uncovered in morning.Storage of culture in canal at night, circulated in basins during the day

*Assumed rectangular open-channel flow, with the characteristic length defined as the cross-sectional area divided by its wetted perimeter. For the conventional raceways, the cross-section height was taken as the culture depth (0.25 m) and its width as 0.53 m. For the ARID pond, the average culture depth (0.175 m) in the shallow basins was taken for the cross-sectional area height and 5 m for the channel width, estimated with kinematic viscosity of saltwater at 35 ppt and 15°C, 1.205e-6 m2 s−1.