White Mouth Disease in Fish

When one buys fish from the local fish store, carefully observe the mouth of the fish and its head for any signs of white patches.

Symptoms

If the fish in the tank behaves in the following manner, it has contracted a bacterial disease. Fish swims with its mouth open like it has a pebble or something stuck in the mouth. Fish keeps swimming at the surface of the water.

If this is the case, remove the fish immediately. At this stage treating the fish is very difficult. The fish does not live for more than 24 hours depending on what stage the infection is in.

This is very contagious and the other fish can get this also. I had purchased a guppy which had this infection. The guppy died eventually. I changed about 80% of the water hoping the bacteria would go away. The next day 2 harlequin rasboras in the tank got the same disease. These were healthy fish and were in the tank for about 3 weeks without any issue. I had to remove these 2 rasbora fish to prevent these from spreading the infection. These 2 fish died in a few hours. Any kind of medicine is pretty much ineffective.


Preventing spread of infection:
The method I discovered was to add aquarium salt to the tank (1 tablespoon or thereabouts per gallon). This kills the bacteria and prevents the other fish from succumbing to this infection.


Avoiding this problem.
Quarantine any new fish before introducing in the aquarium.