it deosnt actually have slides. you just place the microscope on say for instance a rock or tree as your out and about and you look through and there is the tree right up close. its great for all those things that you cant get in a slide..like a living ant or a curved surface. brilliant fun! theres a larger one which we bought which has slides in and its great you can even see salmonella with it whicch is pretty small. This one you won't see bacteria with. nor plant cells but you will see the scales on a moths wing and the flowers on a mold. Hope this helps.
Of course not! Read something about bacteria and items as small (E coli are typically two-thousandths of a millimetre long). It only magnifies to 40x. You need at least 400x for bacteria. This is a pocket microscope for viewing small insects and parts thereof; plant parts etc. from around .5mm (.5mm x 40 = 20mm)
I can't say this is something my son has used this for, but he has looked at lots of plant parts from our garden with good results. You may need something with stronger magnification if you are wanting to look at things in more detail, this is just a child's toy really and serves this purpose very well.
It depends how big the algae are and what detail you want to see. For many of the smaller single-celled algae including desmids and diatoms you really need a transmitted light microscope capable of magnifications between x100 and x400. Although very good for close observation in the field, the pocket microscope has a maximum magnification of x40 which is ok to observe small pond creatures such as Daphnia.