Coralline Algae and calcification

Hey Guys,

I am 4 and half months into my new setup. My rock has some(very minimal) coralline algae growing on the rocks. Thing is,.. thats the same coralline algae that has been on my rock since I bought it and cured it. So being the patient person I am (Not) I've been trying to get this coralline to grow more around the rocks cause I want to add some color ot them. I've just gotten over the green algae phase and my rock has a mixture of light green algae on them, with a whitish look to them, along with some big and small spots of purple coralline. I've been reading that coralline requires HQ lighting, High calcium 460 -480, Ph of 8.2 - 8.4 and high alk 9 - 13 dkh. I've been keeping these parameters within the range. And still nothing, I don't have an alage issue thank god, I just want to get coralline to grow.

I was told by a LFS that I should use/add more mag to my tank. I don't understand how adding MAG would help. Can someone tell me what I am doing wrong?

 

Also how would I know when I have good calcification in my tank.