Here are a few tips that I've read to help with the growth of coraline algae.
Most important keep your levels down nitrates 0. Calcium 400-500 PPM
You must have some sort of coraline algae somewhere in the tank for it to grow and spread.
To speed up the process you might want to try Purple Up I did that and it helped alot but you must test daily for calcium magnesium and alk. and dosing this without knowing what your doing is not advised.
Let the actinics run a few hours before your halide lighting comes on and a few hours afte your halides go off.
Try and keep Calcium levels at 400-500 PPM
I also read this, If you buy a coral or sometype of rock with lots of coraline algae on it you can try scraping it off with your fingers or a credit card or an algae scraper by the power head so it spreads out throughout the rockwork in the tank.
The best advice is be patient it takes time and keeping your levels in check is really the key along with patience patience patience.
Just note coraline algae is beautiful but once you get it in your dt it spreads lke a wildfire and you will be scraping scraping and more scraping.
I hope this helped.