Help with my Pufferfish with a moustache..?

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Hi there, wondering if anyone has any ideas of what I could do to help my Pufferfish
I purchased this guy 3-4 years ago, and just over a year ago I started to notice this growth of weed on his face. It remained for several weeks before disappearing (I didn’t want to touch him as not to stress him out and thought pulling it might do more damage than good)
But now it seems the growth has returned and although he eats no problem I’m worried it’s hurting hum

Wondered if anyone had any advice or if they’d seen this before..?

Sorry for the not so great photo