Growth on guppy fin?

[JonafinJonaphan]

I noticed some bumps/growth on the tail fin of one of the guppies in my 37 gallon. Not knowing much about it, I put him in a QT until I can get a diagnosis. Does anyone know what this is? Is it harmful? He is swimming and eating so it doesn't seem to be bothering him much.

 

[Delapool]

Hello, welcome to the forum

If along the veins / rays of the fin may just be a bit of damage and should eventually go.

If like white salt crystals on the fin, may be white spot.