Live Rock Turning Dark......help

[eyeday]

Hi guys,, i have a 40 galons fish tank and 30 lbs of live rock... i just notice that the top part of the live rock is turning dark brown collor,,, does anyone know why? is the rock still alive? how can i get rid of it? i have a canister fiter i put an extra carbon filter to see if it helps

 

[cranberry]

Is it a new tank?
Does it kindda look like this?

If so, leave it be.... it's Diatoms and will recede in time.

 

[eyeday]

the tanks is almost a year old,,,and yes it looks almost the same as the pic. is that bad?

 

[crypt keeper]

no. add more flow or do more water changes

 

[cranberry]

Did you change lights recently?