Energy for fish to carry on with its biological activities and growth comes from food that they eat. In artificial diets, protein become the most expensive source of energy so it is necessary to keep the proportion of protein down to the optimum levels for good growth and feed conversion. In another study, prebiotics resulted in good growth of fish using a manufactured prebiotic supplement. Ideally, we want food material available all year, inexpensive and not be in competition with food material for human consumption. In this study, food formulation with prebiotics made from local products were prepared for fish food. In this study sago was the source of carbohydrates, mackerel and land snails were the source of protein. The formulation was fed to humpback grouper Cromileptes altivelis to study the effectiveness on its growth. Ninety humpback groupers (size 9-9.5 cm, weight 10 – 11 g) were reared in 3 fiberglass tanks for four weeks. Each tank had 30 fish, first tank as control without sago and the two tanks with sago in dietary prebiotic pellet. Length and weight gain were recorded every week then growth performance of fish were assessed in the form of Specific Growth Rate (SGR), Food Conversion Ratio (FCR), weight gain daily and length-weight relationship. Food proximate test were carried out separately in the Integrated Chemistry Laboratory, Institut Pertanian Bogor. Data analysis showed a significant difference in the growth performance of humpback grouper through the values of SGR, FCR and average growth daily, between treatment A and B (with sago) and treatment C (control, zero sago). The proximate test displayed lower protein in treatment A (57.95%) and B (55.95%) but higher in treatment C (59.37%), in the contrary to carbohydrate for treatment A (27.80%), treatment B (26%) and treatment C (22.98%).

Fish growth is one of the most target in aquaculture with right method of feeding, water quality and size of cages where they were held. In this study, a 70-day research was conducted to evaluate the effect of floating net cages dimension on growth and survival of trevally Caranx ignobilis in Ambon Inner Bay of Indonesia. A total of 90 juvenile trevallies with an average weight of 17.18 ± 1.9 g was randomly stocked in six floating net cages at three different sizes as treatments in replicate groups. Fish were fed 10% of total body mass with by catch fish twice a day to satiation. Length and weight were recorded, growth performance of fish were assessed in the form of Specific Growth Rate (SGR), Food Conversion Ratio (FCR) and Survival rate (SR). The result showed there were no significant different growth rate (SGR) at different treatments (p>0,05), with the highest SR = 100% and lowest FCR = 2.9 both in treatment C. It means the best dimension of fish rare in this research was at the biggest size of cage 200 × 150 × 100 cm 3.

The aim of this research is to determine the amount of trash fish the fish need for growth, and possible saving strategies through reducing the amount of feed until the minimum requirement is reached. Bubara fish C. ignobilis was reared in aquatec floating cages, each cage measuring 3 m × 3 m × 3m. In this study, the fish were reared in four smaller bags, with the size 1.5m × 1.5m × 1.5m placed in one large bag. As many as 75 fish with varying sizes were placed in a small bag, while 20 selected fish were allowed to measure. Fish that are placed in small bags vary in size with a length of 9.56 - 11,125 cm (TL) and a weight of 6.5 - 8.7 g. Each small bag was given different treatments, successively as follows: three day fasting - three day eating (T3), four day fasting - four day eating (T4), and five day fasting - five day eating (T5). Fish are fed 10 -15% of the total biomass, at 8:00 a.m. and 5:00 p.m. daily for 70 consecutive days. Every week, the measurement of waters parameters is carried out to determine the condition of the waters that support aquaculture activities. The results showed that there was weight gainned in the three treatments which were stated based on the absolute growth rate in weight (AGR): 0.65 g.day -1 in T3 treatment; 0.77 g.day -1 in T4 treatment; and 0.80 g.day -1 in T5 treatment. Bubara fish C. ignobilis also had the best survival rates during the rearing period even though they were treated without food with the survival rates of 90 - 95%. The efficiency of feed utilization as stated by the FCR shows that the treatment without food (fasting treatment) can be used as a mode to reduce feed spending. Treatment without food is also able to increase the number of small intestinal villi to expand the absorption surface, so that more feed is used compared to those left to rot at the bottom of the bag.

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