Skin Problems Black dots on fur.

The picture's not visible.

But you can't see mites. They're microscopic, and burrow under the skin.

Black dots may be flea dirt. Put some on a paper towel and put a tiny drop of water on them. If the damp towel turns red (from blood), that's what it is.

Here's some info on parasites. Maybe you can find it there: https://www.guinealynx.info/parasites.html

The picture showed up for me. The fur is white and the dots are dark, but they almost look like lice nits to me.

Yep, look more like lice nits than flea dirt. Are they stuck to the hair shaft? If so, that's what they are.

https://www.guineapigcages.com/forum/threads/111160-How-to-treat-for-mites-and-lice