determined twice a week using EC meter model
HANA instrument conductivity meter HI 8033. Two
100 ml of water were sampled from fish tanks to
determine the pH using Orion model 410A pH meter.
Total ammonia (NH4
++NH3) was measured weekly
(taking two samples of water from the fish rearing
tanks with 10 times dilution, using distilled water)
(Parsons et al., 1984). Nitrite (NO2
+) was measured
weekly (APHA, 1980).
2.4. Fish weight measurement
The individual and biomass of fish were measured
at the beginning and end of the study using
gravimetery and correction for water values.
2.5. The sampling and dry fish weight measurements
Before start of experiment, from each fish group
acclimated with the experimental feed for 1 month,
five fishes were sampled and weighed then cut into
small pieces and were put inside a dry dish. The dish
containing piecemeal fish was put inside an oven at
70 8C, and dry weight was recorded. The samples
were reweighed until getting the fixed weights for
each fish sample; this process was done for fish
sampled at the termination of the experimental period