Cup coral has algae

[alexytman]

Since I started my hobby is have always loved urchins. They function more as astheics as they're not the fastest cleaners. But recently I've started to hate them. My tuxido was knocked over by it. By the time I got to it. Some tips of the lps had algae on it. What should I do?

(Tiny brown coloration under the polyps.)
It's been 10 to 15min since I picked it up. At least it opens. But why did algae grow on it so quickly.? There's no algae except for on my acrylic box near the top of the tank.

 

[alexytman]

. My tuxido was knocked over by it.

I mean my coral was knocked over by my tuxido.

 

[James M]

How long was it on the sand bed ?
Maybe detritus?
Could be damaged / dead tissue algae has grown on.
I would suggest gluing the corals to the rocks