Seaweeds generally have high growth rates when exposed to environments rich in nitrogen and phosphorous. However, they cannot tolerate nutrient rich environments for long periods, causing reduced productivity (Yu & Yang 2008). G. birdiae showed positive SGR values at the surface, during the first 21 days of cultivation and at 10 and 20 cm depth on the 1st and 3rd weeks. Although the values recorded during these periods were positive, they were lower than those found by other authors for the Gracilaria species in integrated cultivation (Nelson et al., 2001; Marinho-Soriano et al., 2002; Msuya & Neori 2002; Chirapart & Lewmanomont 2004). The modest values obtained in this study may also be related to limited water movement in the pond since no aerators or water circulation mechanisms were used. The direct association between water movement and nutrient absorption should be pointed out. In fact, Ryder et al. (2004) demonstrated that the lack of water movement significantly decreases growth rates of Gracilaria parvispora in ponds and lagoons in Hawaii.