The experiment was conducted in the Wet Laboratory of Bangladesh Agricultural University, Mymensingh-2202. Seven days old fry of P. sarana (5.0±00 mrn.and 2.5±00 mg in length and weight, respectively) were stocked in nine glass aquaria (45x25x24 cm each) containing 10L of deep tube-well water. The speed of the water supply was controlled with the help of porous pipe in each aquarium. The experiment was designed with 3 treatments having three replications of each. Sixty larvae were used in each aquarium at a stocking density of 6 fry/L of water and were reared for 35 days.
The diets for the rearing of P. sarana fry in laboratory condition was only live feed (plankton) for T1, only SABINCO feed for -T2 and mixed feed for T3 and were administered twice in a day (0900 and 1800 hrs).
The live food was always kept available for the larvae and the larvae were always fed up to their satiation level. Fifty percent water of each aquarium was exchanged with fresh deep tube-well water once in a day. The fecal output and waste of feed were removed from the aquarium by siphoning. Aeration was provided for 22 h everyday from three air blowers and was stopped for 2 h for feeding and cleaning the aquaria. During cleaning, dead fry from each aquarium, if any, were removed immediately and the number was recorded.
Proximate composition of the feed ingredient was done to estimate the amount of protein, lipid, crude fiber, ash, vitamin and minerals by standard methods (AOAC, 1980).
Ten (10) fishes were randomly collected from each aquarium at seven days interval. The weight (mg) was taken by an analytical balance (College B204S, Switzerland) and the length (mm) was measured by placing the fry in a Petri dish on a 1 mm graph paper. Sampling was done before application of feed to avoid the biasness of weight due to presence of excessive feed.
For the study of both phytoplankton and zooplankton in case of T1, five litres of water samples were collected every week and then passed through plankton net of 55 blotting silk of 100pm mesh size. The collected samples were concentrated to 40 ml and preserved in labeled plastic vials with 5% formalin for further analysis. From the concentrated volume of plankton samples, lml was taken by a dropper and then put on the Sedwich-Rafter counting cell. The counting chamber was covered with a cover slip so as to eliminate the air bubbles and left for a few minutes to allow the plankton to settle-down. Then Sedwich-Rafter counting cell were placed under an electric microscope (magnification-10x10) and both phytoplankton and zooplankton were -counted from 10 random fields (units) out of 1000 units. After necessary calculation, the total number of both phytoplankton and zooplankton was expressed as number per liter. The qualitative analysis of both phytoplankton and zooplankton was done according to Prescott (1964).
Temperature, dissolved oxygen (DO), and pH of water of each aquarium under each treatment were recorded on sampling dates. The temperature was recorded by using a Celsius thermometer, DO was measured by a digital DO meter (Multi 340i/set, Germany) and pH was measured by a portable digital pH meter (MICRO-TEMP; pH 500).
The data obtained in the study were analyzed by one-way analysis of variance (ANOVA), followed by Duncan's Multiple Range Test at a significance level of P<0.05. These statistical analyses were performed with the aid of the computer software MSTATC program.