I have a male guppy who has been acting strange, acting like a loner and not as active as it was.
Last night I noticed a white patch on the front of his head, see attached image.
I'm not sure if this is white spot or something else.
I have a 25l tank, the water is fine from tests. It has been run for three weeks now.
I originally had two guppies, but one passed away when I introduced three minnows to the tank. It died from what appeared to be shock. I got a new guppy to replace it.
I am not sure if this has stressed the remaining guppy out, hence the strange behaviour.
Any ideas please?