go with sand
I will do 1" sand bed
Crushed coral traps lots of detritus and mess up your parameters
CaribSea Seaflor Special Grade. I accidently ordered the Super Reef sand by them which is a mix of Special Grade and crushed corals. Its actually not too bad. I do have two big bags left over if you are interested. Most people in my search I found liked Special Grade or Tropic Eden Reeflakes.