urchins and faux sand beds

[OceanNwisconsin]

im starting a 210 FOWLR, and i have a tahitian moon faux sand bed that i would like to keep black so what urchins are good at getting rid of coraline algae? i like the black long spine. i also plan on getting some triggers and angles to go along with my blue and yellow tang. so the urchin has to be compatible with these.i also have a black cucumber in my current tank and was wondering if it would do bad in the new tank seeing that the sand bed isnt really digestible..

 

[aquaman67]

Urichins IMO just spread coralline.

They chew at it, and the small pieces just float to new places and establish a new spots. They don't wipe the surface clean.