Growth on goldfish head

[Guest Spotta shubunkin]

I’ve a common goldfish with a large bump on his head - tried Melafix Pimafix and anti ulcer a week on each 

The growth has stayed the same sized but shape changes small white lumps on the bump appear and reappear at intervals 

any idea what it might be?

[koko 14,341]

20 hours ago, Guest Spotta shubunkin said:

I’ve a common goldfish with a large bump on his head - tried Melafix Pimafix and anti ulcer a week on each 

The growth has stayed the same sized but shape changes small white lumps on the bump appear and reappear at intervals 

any idea what it might be?

It could be bacterial or an injury. Photos would help a lot in this.