In my opinion i wouldn't use crushed coral. That is how we started our tank and within 2 months out that came and in with the sugar sized. The crushed coral traps all the waste and excess food which then turns into nitrates which then puts you in a new host of problems. We took all our crushed coral out and in with the new in about 3 hours in our 130. We just took all the inverts and fish out and put them in a rubbermaid. Rinsed the sand really well and in it went. Waited for the sandstorm to die down put the rocks back where we wanted then and we were good.
Although just my 0.02cents worth
Craig