Isolation and Identification For isolation, water samples were randomly collected in plastic water bottles and also by dropper in glass vials containing modified Chu-10D medium from different natural and artificial water bodies (e.g. ponds, ditches, sprinklers etc.) located at Dhaka University campus area and Khulna region, during 01 March 2014 to 20 December 2014. Direct isolations were done by picking up single filament or single cell using Platinum wire loop or sterile Pasture pipette. In some cases, series of dilutions were made in sterile medium using homogenized suspension of natural algal samples. Identification of both blue-green and green algae was carried out following cross matching of morphological characteristics as described by Siddiqui et al. (2007) and Ahmed et al. (2008). Characteristics of blue-green alga (Nostoc spongiaeforme) Class: Cyanophyceae Order: Nostocales Family: Nostocacae Genus: Nostoc Species: Nostoc spongiaeforme Description Colony globose when young, later expanding into an irregular gelatinous ball, 2-3 cm in diameter, blue-green in colour, dense peripherally with much contorted trichomes, central portion watery with less contorted trichomes. Trichomes 2.88.7 µm wide. Cells 2.8-8.7 µm long. Heterocysts sub-spherical or oblong 4.2-5.8 µm wide, 4.8-8.4 µm long. Akinetes sub-spherical or ellipsoidal occurring in chains of 3-15, 458.0 µm broad and 5.0-9.0 µm long, wall smooth. Characteristics of green alga (Chlamydomonas noctigama) Class: Chlorophyceae Order: Volvocales Family: Chlamydomonadaceae Genus: Chlamydomonas Species: Chlamydomonas noctigama Description Cells spherical with true cell wall, flagella present. Chloroplasts parietal, massive cup-shaped, longitudinally ridged, pyrenoid usually one, in some cases two or three. Media Composition The liquid medium used in this study is not an absolute inorganic medium but with two organic compounds, the EDTA as a chelating agent and HEPES as a buffer. Sterilization All the required instruments were sterilized at 120°C temperature and 15 lb/sq. inch (10.35 K Pa) pressure for 15 minutes. Culturing of algae After identification, isolated microalgae were used as inoculants for algal monoculture. Identification of species followed by the genus was done with the 4, 8 and 15 days old monoculture. In vitroalgal culture was done in modified Chu-10D culture medium (Sinclair and Whitton, 1977) incubated in the controlled growth room, at 23 to 28ºC temperature in an average light flux of 71 µEm-2s-1. Media Composition The liquid medium used in this study is not an absolute inorganic medium but with two organic compounds, the EDTA as a chelating agent and HEPES as a buffer. Sterilization All the required instruments were sterilized at 120°C temperature and 15 lb/sq. inch (10.35 K Pa) pressure for 15 minutes. Maintenance and subculturing Stock cultures were maintained in 60 ml liquid medium incubated standing in an average 25°C growth room under continuous light (ca 40 µEm-2s-1.). Subcultures to fresh medium were made after about three months. Stocks for experimental purposes were maintained at 32°C under continuous light of average 71 µEm-2s-1. Estimation of growth Total chlorophyll and optical density (O.D.) have been used to estimate growth. During early stage of growth, the whole contents of each flask were used for either total chlorophyll or O.D. Chlorophyll a(for blue-green alga) was estimated by following the procedure based on the recommendations of Marker et al.(1980). Chlorophyll a and bcan be calculated by following formulae according to APHA (American Public Health Association), 1985. By measuring the optical density at 750 nm growth was estimated using a spectrophotometer as described by Rodolfi et al., 2009. During early stage of growth, the whole contents of each flask were used for O.D. The need for clean and low-cost algae production demands for investigations on algal physiological response under different growth conditions. Experiments were carried out in batch culture under continuous light. In the growth room illumination was provided by white fluorescent tubes (average 71 µEm-2s-1.) above and below the alga. The flasks were usually randomly rearranged at 24 h interval. The temperature was set at a range of 24 to 26 ºC. pH Seven pH values (i.e. 5.0, 5.5, 6.0, 6.5, 7.0, 7.5 and 8.0) for GA and five pH values (i.e. 6.5, 7.0, 7.5, 8.0 and 8.5) for BGA had been used to find out the optimum pH value for respective algal growth in the medium. Temperature The growth of both GA and BGA was observed at four different temperature (i.e. 20, 25, 30 and 35 ºC) to find out optimum temperature for respective algal growth in the medium. Light intensity Five light intensities (i.e. 30, 50, 70, 90 and 110 µEm-2s-1.) had been used to find out the optimum light intensity for the growth of selected algal strains. Vitamin supplements Four vitamin solutions, individually (i.e. B1, B6, B7, B12) and in six combinations (i.e. B1+B6, B1+B7, B1+B12, B7+B12, B1+B7+B12 and B1+B6+B7+B12) had been used to find out the effect of vitamin for two algal growths in the medium.