New 40 Gallon FOWLR Setup - CC or LS?

[joebrooklyn]

I know 40 gallons is on the small side for a saltwater setup, but I want the challenge of keeping up a saltwater tank. I'm leaning towards a FOWLR setup and was wondering should I use crushed coral or live sand as a substrate.
I have a wet/dry filter and protein skimmer, so far and I'm ready to purchase the proper substrate upon getting advice from you experts

 

[geridoc]

I have used cc for 35 years, so I am speaking from experience when I say "get sand". cc traps detritus that decays and turns into nitrates, and it limits the fish you can have (forget burrowing wrasses, etc). My kids tell me that I'm old fashioned, and I probably am, but the "newer" substrate, sand, is clearly superior.