Well it looks like there is somewhat of a dent in the head and its a whitish color in the dent. there is also something on her scales on the other side of her looks like a very small sliver that is dark. I just lost the other krib to columnaris, and if this is a bad disease i am gonna throw her out too, i currently have three rummy nose tetras in the tank who look healthy. If I decide to throw her out. what should i do with the water to make sure its not gonna affect my other fish. I will restock it wtih some of their fry from before.