Fin rot is caused by bacteria that are always present in aquarium water. Fish become susceptible to fin rot when they are kept in poor water conditions, and it is common on fish kept in unfiltered tanks or bowls. The reason is that your pet is being forced to swim in water that is contaminated by its own feces which is essentially ammonia. If left untreated, the disease will erode the fins, especially the tail, and can enter the body of the fish, causing death. Symptoms include loss of fins and white and red patches on the fins.
Detecting fin rots
Early detection of the illness is the best to try and prevent further fin damage. First know that clear or whitish tips on your betta's fins and tail is fin re-growth, which is a very good thing. If your betta has dark brown/black tips, holes, or tears in his fins that appear to be getting worse, they most likely have fin and tail rot.
In a worst case scenario, the fins and/or tail could be falling apart, shredding, or be completely missing.
Once Fin Rot is diagnosed, what to do next
If you caught the onset of Fin Rot quickly, it could be as easy a fix as simply changing out the water and gravel. A lot of times that is all that is necessary. However, if your betta is in a more advanced stage of fin rot, then there is a process that you will need to go through.
Here are the steps:
1. Nuke the tank or bowl aka Take out everything and wash them entirely (Note: No soap)
2. Apply some form of fungus eliminator to the water. (Can be gotten from LFS)
3. add 1/4 to 1/2 teaspoon of aquarium salt per gallon of water. (This is to hold the bacteria back and thus increase the healing speed)
4. Upon seeing whitish color on the fin tips signal fin regrowth. Continue large water change every week. Or small water change every 2 days.
Note: Remember to wash your hand before and after handling the fish or the material.