Magnification

What microscope do you need for pond water micorganisms?
While colonies of protozoa can be viewed using 30X on a stereo microscope, other microorganisms such as hydra and daphnia can actually be seen without...
Which magnification would be most suited for scanning a slide to find a certain object?
Why do you need to start with 4x in magnification on a microscope? The 4x objective lens has the lowest power and, therefore the highest field of view...