I am working on diatom profiling from a water body where drowning deaths are known recently. Profile includes comparative analysis between different genus of diatoms.
You may want to consider making permanent slides as it is likely that you will not be able to id the diatoms to species level using a Sedgewick-Rafter. I would recommend mounting the diatoms in a suitable mountant such as Naphrax which has a suitable refractive index for studying diatoms.