Prevent it by dealing with the source of the moisture, which is likely the shower if it's only in the bathroom. If you have a bathroom exhaust fan, use that during and after showers. Opening a window can help if you don't have one.

When my vent fan died last winter, I used a small dehumidifier because the moisture got really bad. Dehumidifiers take a fair bit of energy, but that energy is converted to heat, so it's basically the same as using electric heat.

[–] DamarcusArt@lemmygrad.ml 3 points 4 months ago

I've had major black mold problems in my current place since I moved here years ago, but this year I got a dehumidifier and it's helped massively. The mold isn't completely gone, but it's only about 10% of what it was.