Curing Live Rock

Would a 1 pound rock in my 29 gallon that isn't cured harm my water
conditions enough to worry about? It had some growth but that has fallen off
and the rock itself looks like its covered in white rotten looking stuff.

Also I have some ammonia in the tank should I do water changes just like I
would in a fresh water tank or is there something I could add that would
counter act the ammonia?

Thanks
Kelly