How to bounce back this hammer?

[zach_jb69]

I got this hammer coral from petco and it looked a little better than this when i had got it but over months it just got worse until this. Tissue loss, polyp receding skele covered in alg.

 

[NonstopSoda]

What are your parameters, lights, and flow. For now i suggest keeping it clean from algae at the edges of the skeleton with a brush.