I saw crushed coral (roughly 1" x 1/4" ) in a LFS. It was very white in color. What is the advantage/disadvantage by putting it into the tank? Should it be processed before putting it into the tank? How?
I would advise against using it. It will collect detritus and lead to nitrate issues. An aragonite sand is a much better choice. Caribsea makes fine products. I use their Fiji Pink sand. Teh Aragamax Select products are very good as well.
Crushed coral is usually regarded on reef central as bad stuff. It does however prove to be a usefull component of a plenum set up. I have a plenum in my 46gal bow and it does use crushed coral. I will set up a plenum in my 35gal hex I'm working on now and my future 125gal. As far as using it as your only substrate, it can lead to nitrite-nitrate problems and generally just looks nasty after a whhile.