This study has been carried out to investigate the growth performance and
economic efficiency as well as pond productivity of Nile tilapia (Oreochromis ni/oticus)
and silver carp (Hypophtha/michthys mo/itrix vaL) reared in polyculture earthen ponds
as affected by different fertilizing inputs. Nile tilapia and silver carp fingerlings
averaging 0.5 g in weight were assigned randomly to two tested different fertilized
inputs. Two treatments were applied in the earthen ponds. (T₁) fresh blue green
algae at a rate of one collecting algae pond (3kg) every day/fish pond (5 days 1 week)
and (T2) fertilization with chicken manure 25 kg 1 pond every 2 weeks. Four earthen
ponds each measuring 20x50 m were used in the experiment. Each treatment was
performed in duplicate. All the ponds were stocked with 2500 tilapia plus 500 silver
fish 1 pond (12600/feddan). The study extended 90 days. Results obtained can be
summarized in the following: 1- The highest final body weight, average daily gain
(AOG) and specific growth rate (SGR), were recorded for Nile tilapia fish group in T₁.
While a reverse trend was observed with silver carp which exhipted the highest final
body weight, AOG and SGR with Tz. 2- With regard to economic efficiency, the total
cost of T2 was higher than Tl but a net return of Tl was higher than T2. In conclusion, the use of fresh blue green algae in fish pond culture could be
recommended for Nile tilapia and silver carp at a rate of one collecting algae pond
(3kg) every day/fish pond (5 days 1 week) with stocking density 126001 fedd.
Especially with the problems found now for poultry manure.