Black spots brush away like dust or get sucked up by the vacuum

[Nitedr]

My FC holds well and I don't have any green or mustard algae.

The black spots in the pic brush away like dust or get sucked up by the vacuum. Sometimes I think its dust that settles in crevices in the plaster and sometimes i think its black algae.

Any help would be greatly appreciated.

 

[JasonLion]

What you describe sounds like simple dust. Black algae won't vacuum up at all, and responds only to the most vigorous brushing.

 

[Nitedr]

Thanks for the reply. Sorry about posting in someone's thread. Didn't mean to hijack the thread but i figured since it was in line the topic it would be okay.

 

[JamesW]

Do you have a salt system?