Yield of C. crispus did not differ significantly when grown at two different stocking densities (5 kg m−2 and 8 kg m−2 ). On the other hand, Gracilaria had significantly higher yields at 5 than at 7 kg m−2 . Better NUE, on average 76.7% (± 22.13%), was also obtained with 5 kg m−2 stocking density and only 63.8% (± 24.62%) with 7 kg m−2 . The yield of Gracilaria increased significantly with the increase of water flux from 140 to 325 l h−1 and more nitrogen was removed from the water. However, NUE decreased from 48.4% to 33.4% at 140 and 325 l h−1 , respectively. Biofiltration was highly improved by a cascade system with a NUE as high as 83.5%.
Gracilaria grew year round, but also performed better during spring/summer, producing an average