Help Please

[lazyfish]

Hi ,

I have a Dalmation molly that has turned almost totally black. It happens to be one of my favourite fish and exist in my tank because a friend picked it out for me and essentially it is his fish. I need help because recently this fish has developed a bump on his head picture to follow. The fish isn't affected by it and it eats and swims normally. my ph and amonia levels are fine and none of the other fish have any issues. I have added aquarium salt to my water in a water change in hopes that it might help. I am lost and need assistance. Please help me.
:goldfish:

10 Galon tank established for over 1 year no new fish added. Other orange molly and dano are fine along with upside down catfish.

[Lady Hobbs]

Aquarium salt does not make a brackish tank. A brackish tank is Marine Salt.

But he doesn't have to have salt. How much did you add?

[lazyfish]

I added 1 1/2 tsp / 10 gal. I prefer to go under than over salt. The fish seem happy after water change and new plants including their favourite Money wart. I just wish I knew what was going on with that fish.
He is a very nice fish and keeps order in my tank.