The three species were apparently efficient in removing nutrients, mainly nitrogen, from the water, but the green algae (Ulva spp.) removed nutrients more rapidly than the red alga (G. birdiae). After one day of cultivation, 81.9 ± 6.3% of the ammonia (NH3) was removed in tanks containing Ulva, and by the third day, 89.1 ± 4.7% of the nitrate (NO3–) was removed. After five days of cultivation, 98.2 ± 3.7% NH3 (H = 1.1; P = 0.56) and 98.4 ± 3.0% NO3- (H = 2.7; P = 0.25) and 62.1 ± 0.0% of phosphate (PO43-) (H = 0.0; P = 0.90) were also removed by the three macroalgae