A feeding trial was conducted to evaluate the effects of two different sizes of extruded pellets (EP) (EP 1 -3 mm or EP 2 -5 mm) and a moist pellet (MP) in olive flounder, Paralichthys olivaceus, reared in semi-recirculation system. A total of 450 fish with an average initial weight of 5.0 ± 0.2 g (mean ± SD) were fed one of the three experimental diets in triplicate groups. At the end of a 6-week feeding trial, weight gain, specific growth rate, and feed efficiency of fish fed EP diets were

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... nificantly higher than those of fish fed MP (P < 0.05). Water quality parameters like turbidity, total ammonia nitrogen, and total phosphorous from tanks of fish fed EP 1 and EP 2 were significantly lower than those from tanks of fish fed MP. Blood plasma glutamic oxaloacetic transaminase and glucose concentration were significantly higher in fish fed MP diet compared to fish fed EP diets (P < 0.05). Whole body crude protein contents in fish fed EP diets were higher than those from the fish fed MP diet. Whole body amino acid content like threonine, aspartic acid, serine, tyrosine, and cystine were found to be significantly higher in fish fed EP diets than those in fish fed MP diet. In considering overall performance of olive flounder, EP 2 diet could be recommended for the successful aquaculture of this important fish species.