The study explores the nutritive value of fiber in supplemental feeds for milkfish. The feeding rates were adjusted so that all treatments involved equal protein-N load (6 g·kg^-1 fish/day), and varying energy and fiber loads. Rice hull provided the bulk of dietary fiber. Fresh chicken manure, containing 16% protein, served as control. Four 800-m² earthen ponds divided into four compartments were used. Milkfish juveniles (29 g) were stocked at 7,000·ha^-1. After three months of culture, milkfish growth and production and protein efficiency ratio were significantly higher (α = 0.05) in fed ponds than in manured ponds. Average yield and manure conversion ratio in manured ponds were 436 kg·ha^-1 and 14.5, respectively. There was no significant difference in yields (600-624 kg·ha^-1) between feed treatments. Fish exposed to low protein/33% fiber diet had a worse feed conversion ratio (5.8) than those exposed to high protein/15 or 24% fiber diets (3.6). The results indicate that energy was not limiting in the high fiber (24%) treatment compared to low fiber (15%), but additional fiber (33%) did not further improve growth; and fiber in low protein diets was utilized further as a direct or indirect source of energy. Thus, a low protein/high fiber diet can be an economical way of increasing milkfish production in brackishwater ponds.