Nothing in life is guaranteed, but I’d be surprised if it turns out to be something else.
This what makes it so invasive and obnoxious as Tamberav described it (which is very accurate description).
There are mainly 2 ways to defeat it - either by catching early on and eradicating it manually, or using algaecides such as Flucanazole which is extremely effective against it.
I wouldn’t rush to use algaecides though, at least not unless it is a loss cause.
For now, given that it’s on your sand - I’d simply siphon it out. Than, I’d also closely inspect your tank for any other small specks of it and treat any of them immediately by applying either high PH paste (kalk/NaOH or some commercial Aiptesia control product which is essentially the same), or applying some cyanocrylate over it.