^len^aWeigh gain, length, and survival of Pacu (Piaractus brachypomus) larvae were analyzed after they were fed one of four diets. At 36 hours post-hatching larvae were fed for the first time and during three consecutive days: Artemia salina nauplii (T1), wild plankton filtered to 200 microns (T2) , concentrated powder with 48% crude protein (T3) or no diet (fasting, T4). Animals were kept at a density of 70 larvae per liter. Statistically significant differences were observed with respect to the final weight for T1, T2, T3, and T4 (2.2 ± 0.3a, 1.7 ± 0.3b, 1.5 ± 0.3bc, 1.5 ± 0.2c mg, respectively) , final length (6.37 ± 0.29a, 0.20b ± 6.16, 5.95 ± 0.27c, 0.26c ± 5.87 mm, respectively), weight gain (0.77 ± 0.39a, 0.31b ± 0.34, 0.16 ± 0.37bc, 0.08 ± 0.21 c mg, respectively) and length gain (0.39 ± 0.17A, 0.18 ± 0.15b, 0.16c ± -0023, -0102 ± 0.15c mm, respectively). The T1 diet had the best results for optimal growth, followed by T2. The survival rate was not statistically different among treatments. These data suggest that the initial diet composition can affect subsequent growth characteristics of Pacu larvae.^les^aSe evaluo la ganancia de peso, la longitud y la supervivencia de larvas de cachama blanca (Piaractus brachypomus) alimentadas con varias dietas. A las 36 horas post-eclosion las larvas se alimentaron por primera vez y durante tres dias consecutivos con nauplios de Artemia salina (T1), plancton silvestre filtrado a 200 μm (T2), concentrado pulverizado con 48% de proteina bruta (T3), o ayuno (T4). Los animales se mantuvieron a una densidad de 70 larvas por litro. Se observaron diferencias estadisticas significativas (p<0.05) con respecto al peso final para los tratamientos T1, T2, T3, y T4 (2.2 ± 0.3a; 1.7 ± 0.3b; 1.5 ± 0.3bc; 1.5 ± 0.2c mg, respectivamente), longitud final (6.37 ± 0.29a; 6.16 ± 0.20b; 5.95 ± 0.27c; 5.87 ± 0.26c mm, respectivamente), ganancia de peso (0.77 ± 0.39a; 0.34 ± 0.31b; 0.16 ± 0.37bc; 0.08 ± 0.21c mg, respectivamente) y ganancia de longitud (0.39 ± 0.17a; 0.18 ± 0.15b; -0.023 ± 0.16c; -0.102 ± 0.15c mm, respectivamente). El T1 presento los mejores resultados, seguido por T2. El porcentaje de sobrevivencia no tuvo diferencia estadistica significativa entre tratamientos.^lpt^aForam utilizadas larvas de pirapitinga (Piaractus brachypomus) foram mantidas em densidade de 70 larvas/L. Por tres dias consecutivos, as larvas eram alimentadas com nauplios de Artemia salina (T1), plâncton selvagem filtrado (200 μm) (T2), racao em po com 48% de PB (T3) e o tratamento controle era mantido em jejum (T4). Os resultados mostraram diferenca significativa (p <0.05) no peso final (2.2 ± 0.3 a; 1.7 ± 0.3 b; 1.5 ± 0.3 bc; 1.5 ± 0. 2c mg.), no comprimento final (6.37 ± 0.29 a; 6.16 ± 0.20 b; 5.95 ± 0.27 c; c 5.87 ± 0.26 mm.), no ganho de peso (0.77 ± Um 0.39 a; 0.34 ± 0.31 b; 0.16 ± 0.37 bc; c 0.08 ± 0.21c mg.) e no ganho de comprimento (0.39 ± 0.17 a; 0.18 ± 0.15 b; -0.023 ± 0.16 c; -0.102 ± 0.15c mm). Os tratamentos T1 e T2 mostraram os melhores resultados em relacao aos parâmetros anteriormente citados. Contudo, nenhum tratamento mostrou diferenca significativa na porcentagem de sobrevivencia.