When it comes time to look at the various diseases that can affect the guppies one of the common ones can be fungus. This can affect the various parts of the guppy.
Guppy mouth fungus:
One area that can be affected is the mouth and this is called mouth fungus. Unfortunately it can bring the death to the guppies quickly and it has to be dealt with properly. The first thing is making the proper diagnosis of your guppy so that you know what you are treating.
What you will note is that there may be a small white prominent area around the mouth which is stopping the guppy from being able to close its mouth. What will happen is that the entire mouth of the fish becomes filled with a spongy looking substance which in turns leads to the death of the fish.
If you had the opportunity to look at this spongy white substance under a microscope you would see that there are a large amount of moving organisms within it. This growth not only affects the mouth but it eats away at the tissue. What used to believed to be happening here is that this growth of the fungus is stopping the guppy from being able to eat and therefore it will end up starving to death. That used to be what was believed but what has been determined now is that it is not the lack of food but the lack of the water being able to stream through the mouth and out of the gills that is actually the cause of death. If you are noticing that your guppies seem to be very lethargic and are staying near the surface water of the tank then immediately look at them closely to see if they have developed a mouth fungus.
You may notice a tiny spot on your guppy and out of this spot there seems to be small tiny threads radiating upward and outward. It almost looks like a small crown has been placed on the guppy. This is called Crown fungus and when you look at the the rays that are emanating from it they can grow to about an eighth of an inch long before they are brushed off. This again is another type of fungus that you want to treat quickly.
Fin and tail fungus:
You may see a grey or white area forming around the fins and/or the tail of your guppy and it seems to be giving them problems with their swimming action. This will usually occur more often when the guppies are being kept at a temperature that is too cool for them.
Generally speaking fungus diseases were usually only attack the guppies that are weak and this weakness could be from damage to their skin or gills. They may have previously had a bacterial problem that was cleared but the bacteria left some lingering damage which has made them prime for a fungus to occur. Also keeping the water too cold is a big factor that has to be watched closely.
Saprolegnia fungus is one that can create death in the fry and death can occur before the symptoms even show.
No matter which form of fungus your guppy is dealing with they each demand immediate and specific treatment for the actual fungal condition. Your local aquarium shop should have a selection of products to use for you to treat your fish with, but again it is highly important that you are able to identify which fungus you are dealing with so that you are sure to get the proper treatment.