What is this things on my backwall

[HumbleAsianReefer]

Hello guys. Can anybody tell me what is this? Thanks in advance

1st, my 15g quarantine tank. Age around 4months. Tiny white dots all over backwall.

and this one, my other quarantine tank. But this one is more like a fade whitish patch, age around 7-8months. Not sure if u guys can see it clearly

 

[Kasrift]

Spirobid worms, beneficial filter feeders and no problem.

 

[HumbleAsianReefer]

Spirobid worms, beneficial filter feeders and no problem.

Ohh okayy. Thanks bud, appreciate it