Grey Matter

[Wardcarrie5]

I have this grey/white matter growing on substrate I be tried to vacuum up but it keeps growing back. My levels are all fine

 

[Dallascowboys16]

I have this grey/white matter growing on substrate I be tried to vacuum up but it keeps growing back. My levels are all fine

Appears to just be mulm which usually accumulates from organics breaking down in your tank. Keep doing good gravel vacs and keeping up on your tank maintenance and it should go away.

Do you have rocks in the tank? If it is a new tank without time for mulm to accumulate it could be dust/debris coming off of the hardscape.