What are these marks on my betta's head?

[Naznaz]

View attachment 93989
My betta hasn't had any marks on his head until today. The marks seem to have developed overnight. Another thing that concerns me is that he spends most of the time swimming around the bottom of the tank. He's still very responsive to food and doesn't seem to have problems swimming or breathing though. Can it be scale rotting or some other disease? What do you guys think it is and what should I do about it?

 

[Colin_T]

Hi and welcome to the forum

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How long has the tank been set up for?
How long have you had the fish for?

How often do you do water changes and how much do you change?
Do you gravel clean the tank when you do a water change?
Do you dechlorinate the new water before adding it to the tank?

What is the ammonia, nitrite, nitrate in the tank water?
What sort of filter do you have?
How often and how do you clean the filter?

Have you added anything new (fish, plants, wood, etc) to the tank in the 2 weeks before this started?
Do you add plant fertilisers, supplements or anything else to the tank?
Are there any other fishes in the tank?