Found this as well..describes in detail..
One of the earliest symptoms of Fin Rot is that the fins start appearing ragged. As the disease progresses, the fins become increasingly shorter. Whiteness can be observed at the edges. Cotton Wool, which is a secondary disease may start developing and will manifest as a fuzzy growth on the fins. If untreated, the base of the fins will start becoming red and inflamed, with bloody patches resulting.
Fin Rot is most often caused when the Betta are distressed due to poor water quality, overfeeding, expired food, overcrowding and rough handling. If the water is not changed regularly, the leftover food particles and feces will decompose and contaminate the water. If there are too many Betta in the tank or if too much food is placed in the tank, even regular water changes may not prevent the disease. The resultant stress on the Betta, lower their immunity thus making them very susceptible to attack from the bacteria present in their water. Only in very rare instances will Betta develop Fin Rot in spite of an impeccably maintained tank.
Once Fin Rot sets in, a complete change of water and a careful examination of the conditions within the aquarium will be required. Take everything out of the aquarium and wash all the decorations and pebbles with hot water. Do not use soap. Follow instructions for changing the water in the aquarium.
Fin Rot is a bacterial infection and medication is available to cure it. Some medications that have been successfully used to cure fin rot include Jungle Fungus Eliminator and Tetracycline.
Fin Rot is contagious. Fish that appear uncontaminated should be separated from the fish that appear contaminated. It is advisable to place the apparently uncontaminated Betta in a separate quarantine tank until you are very sure that they are healthy. To prevent the disease from being transferred to your other healthy Betta, do not share nets between the tanks. Also ensure that everything used in handling either the sick or the quarantined Betta are washed properly in hot water before being used for any other fish.
Water & Habitat: The water in the tank should be changed every one to two weeks with all decorations, pebbles etc. thoroughly cleaned. It is also important to check the ph and the temperature of the water on a regular basis. All fish, particularly those with long flowing fins such as the Betta, have a tendency to contract Fin Rot when the temperature of the water is either too low or too warm for sustained periods of time.
Food: Check that the food you are feeding your fish is fresh and do not overfeed. It is far better to give your fish smaller quantities of high quality fresh food. Feeding your fish too much food at one time means there will be excess left over food in the water, which in turn will increase the concentration of bacteria in the water.
Handling: Be gentle and cautious when handling Betta. They are easily stressed if they are carelessly handled.
Keeping the habitat controlled, clean and stress free is the best way to ensure Betta's continued health and the Betta owner's continued enjoyment of this beautiful, showy fish.