Algae issue - stuck to rock

[k2-]

So a friend of mine gave this to me and I thought it’s a calcified kind that will look good on my tank. Now it’s on the rocks and so deep rooted that It pulls a 20 pound rock up in the air.

tried Kent m magnesium and it died down a bit only to come back stronger.

high lighting is used just to take photo

 

[G Santana]

What are your nitrate and phosphate readings, high readings make it stronger and harder to remove. I had a bad patch like that and I got my numbers down and used Vibrant once a week and hydrogen peroxide daily for 7 weeks, eventually it started to turn gray and then I just syphoned it all out.
It took time but it worked.

 

[k2-]

Okie so figured a little - phosphate were off the roof . .46 , I changed my refugium recently and it has again started a kind of ugly phase which should last for few weeks. However phosphates are back at .06 after 72 hours ….. however the algae is still waving strong - but I think in few weeks it should get back in check