[HeavyUser]

I purchased 2 Ottos last week. A few days ago I noticed a white mark on the smaller one's head.

I don't think this is a parasite or fungus but I am not sure as I haven't kept fish in a long long time. I think it may have scratched itself on some of the lava rock as there is tons of it in my tank.

What do you guys think it is?

 

[AWolf]

I think it's just pigment. UNless it is bulging or offset from the head somehow. Otos get more whitish colorations all over as they get older. You can name him 'spot'.