Why isn't my coraline algae growing!

[Timbits]

So I have a 40 breeder mixed reef, mostly LPS, zoas, palys, softies, and a few sps. I have around 50 lbs live rock i think and 50 lbs live sand. Tank has been running for around 5 months.

I haven't had any coraline algae growing since my tank was set-up. My rocks look so ugly! Rocks look pretty much the same as when i introduced it to the tank and no coraline algae growing on the glass! Added some coral with coraline algae that covered the rock it was on but it seems that they are fading away.

Don't really know what's going on. I really want the coraline algae to cover my rocks, they look so bare and ugly. Checked my calcium and alk and ph and everything was good with calcium maintaining at 440.

I know my tank is a bit new but i thought coraline algae grew faster than this. Does anyone have any suggestions or comments? Thanks.