The 25MM and 16MM lenses were unable to see plankton

Hey, friend, I have encountered a problem, I follow the microscope made by the author and it can not magnify to see the creatures in the water, may I ask what is the problem? The lens I use is a combination of 25MM and 16MM, I can not use it correctly, may I ask what is the error, what is the problem?

It is so big that I can't see living things in the water