Rust or Algae?!?!?!

[Legit Fish]

i have started noticing some sort of rusty looking algae on my glass very close and under the gravel and is now growing in patches on my substrate. i have ada aqua soil and i feel like it is possibly having a reaction to something?? don't know. this tank is not newly setup. it has been running for more than a year and i was just curious what is the rusty looking "algae" really is.... is it bad? especially for shrimps because i plan on adding shrimps by tomorrow!! please help!

ammonia nitrites nitrates 0 and ph 6.8

 

[Fishey bricks]

Could you post a pic?

 

[Legit Fish]

its hard for me to post a pic due to technology but i will try my best

 

[Fishey bricks]

its hard for me to post a pic due to technology but i will try my best

Ok, with out a pic my guess would be that it's diatoms.

 

[B-Chrono]

+1 on guessing it's a diatom bloom.