Effect of Phytoplankton (Chlorella vulgaris and Scenedesmus spp.) Inoculation on Water Quality for Tilapia Culture by Urea and Superphosphate

Abstract

In this study fingerlings of tilapia hybrid (Oreochromis niloticus x Oreochromis aureus) were cultured in 18 glass aquaria (75 x 40 x 60 em) and two species of phytoplankton (Chiarella vulgaris & Scenedesmus spp) were used.

The investigative experiment included six treatments, each in three replicate aquaria. The first treatment was fertilization by urea at the rate of 435 mg commercial urea I aquarium. The second was the same use of urea plus the addition of phytoplankton at the rate of 5Xl04 cells/mi. The third treatment was fertilization by mono superphosphate (MSP) at the rate of 830 mg commercial MSP I aquarium. The fourth treatment was the same use ofMSP plus the addition of phytoplankton at the rate of 5X104 cells/mi. '1'he fifth treatment was fertilized by urea and MSP mixture at the rates mentioned above for - each. The sixth treatment was the control one without any fertilization or phytoplankton application.

Phytoplankton played an important role in removing ammonia and nitrite from the water milieu, thus providing fish by more healthy conditions to grow.

The average of individual fish body weight (ABW) in the urea+phy. treatment at the end of the experiment was (29.37 ± 0.60 g) which was significantly (P<0.05) greater than that of control (25.22 ± 0.84 g), and the other treatments. The fish in urea treatment had the lowest value of ABW (19.22 ± 1.30 g), this is ascribed to the elevated values ofun-ionized ammonia (NH3) and nitrite concentrations in the water in this treatment. On the contrary urea+phy. treatment had the lowest values of un-ionized ammonia and nitrite '• due to phytoplankton uptake ofthe nitrogenous compounds (urea in this study)

from the water milieu, consequently, transforming it to more appropriate medium for fish growth.