We are using BG-11 and BBM medium to grow but not getting a diversity of algae only Chlorella or Scenedesmus survive in these two media. please suggest any other media.
I am suggesting to perform the ion chromatography analysis or possibly total soluble organic carbon analysis on the samples from actual habitat of these algae and find a media or make a new recipe which accords with your analysis.
You should notice that some of microalga are depending on vitamins and proteins. So, in my opinion, you should try some enriched media, or you can add enrich your media (even same BG11) with a vitamin mix.
Nutrient medium for growing algae isolated from environmental samples is a bit tricky. All the nutrient medium contain common elements with change in the quantity of addition. I suggest you to alter the A5 trace metal mix with different concentrations so that you can get your desired algae.