Strange spot on swordtail fish's head?
Hello, one of my swordtail fish (a cross between a swordtail koi and a regular swordtail, by the way) has had a strange spot on its forehead for about a week. It doesn't look healthy to me, and I don't know what to do. If anyone knows anything about this and could give me some advice, that would be great.
Hello,
this looks like a mechanical injury which, with very good water hygiene, is usually cured by itself. But you should still observe it and if it is fun to treat it medicamentally!