Ocean Rock Going Yellow

[troy007]

myocean rock is going yllow how do i stop it cheers troy

 

[Colin_T]

what do you mean by yellow? is the rock actually changing colour or is it getting a yellow growth on it?
Can you provide a picture of the rock?
Is there a light on the tank and how long is it on for?
How long has the tank been set up for?
Are there fish or invertebrates in the tank?