Why is my rock only green

[Mike7744]

I've had this rock for 3 years in different tanks. (Now in a 125) I started with 40 lbs of live gulf rock after some time I added 45 lbs of CaribSea dry rock. I have never been able to get any coraline algae to grow on the rocks. Everything is green. Even the live rock pieces are mostly green. What can I do different? This is a fowler tank, no inverts, predator fish only.
Here are my parameters
Ph - 8.0
Ammonia- 0
Nitrite- .1
Nitrate- 50
Alkalinity- 7.8
Calcium- 459
Phosphate- .25
Magnesium- 1200

I have tried purple up, but that just put my calcium up high. I was dosing calcium and Alkalinity very little, but saw no change.

Any ideas?

 

[KrisReef]

You need a seed of purple coralline algae, a snail would work. Personally, I would not bother because scraping coralline algae is a huge time waster. Trust me, be happy.

 

[Lavey29]

I'd be more concerned about the aptasia then the green rocks.

 

[CHSUB]

Fish only predator tanks Ime, in general, don’t have the conditions that favor coralline algae; which are low nutrients and palatable algae grazing inhabitants. Your rocks look typical of what I would expect and actually pretty interesting looking…

 

[indigocorals]

We have noticed that lighting can play a big part in growing coraline and water flow. A light fixture meant to keep corals healthy would also help grow coraline on your rocks.

 

[Mike7744]

I run a t5 fixture for lights, have good flow