This is an excellent article written by 3 vets (Roberts, Palmeiro and Weber) that covers:
Bacterial infections, what pre-disposes fish to get them, the primary and secondary causes
The treatments and dosages of antibiotics for different bacterial infections
How to prepare a slide for use under the microscope, gill biopsies
Identifying parasites - ciliated protozoans, flukes and crustaceans
This article does include information about other species of pet fish, but the vast majority of it pertains to Koi.
CLICK HERE to read and download a copy.