Fungi can be interesting to observe, but not all of them are healthy and molds that have spoiled food are particularly a problem.
If you look for a general-purpose mounting medium for making permanent slides, then I recommend Euparal.
Mounting media for making permanent slides can be classified into solvent-based and water-based mounting media.
Alcohol is a solvent of choice for preserving specimens. Alcohol, however, causes some specimens to shrink.
Pond water is a favorite sample to observe. Sometimes, you do not see anything, however. The reason is usually that you took a sample from the water itself and not of the ground.
A drop of inorganic fertilizer greatly enhances the growth of algae in a mini-aquarium.
When mounting permanent slides, it is sometimes possible to observe a clouding of the mounting medium surrounding the specimen. When observing the slide under the microscope, one can see that the clouding is due to many small bubbles, which start to appear.
Making permanent slides can be very easy, not much different than making a wet mount. Making permanent slides can also be a time consuming and lengthy process, stretching over several days, and requiring much lab work. As so often the case: It all depends on the specimen.
There is no single recipe for making a permanent slide, as the preparation process depends much on the nature of the specimen and the mounting medium used. I will only give a generic overview of the process, which has to be adapted to the specific specimen.
Some specimens are thick and require much water. Here are some possibilities on how to do this, without spilling the water over the corner of the slide.