Do you have any to begin with?? Coralline algae doesn't "develop" like beneficial bacteria..... it has to be introduced to the system from an outside source, like hitchhiking in on a coral frag or LR
Like Mrc stated, if you don't have a lot of stony corals that consume your calc & alk
, then regular pwc
's will maintain plenty good enough levels for it to grow. If you have some, the best way to get it to spread is shut off any filtration and scrape it, leaving a powerhead or two on for about an hour to spread the scrapings, then turn your filtration back on. It can take a while to get going, but once it does it usually takes off.