Using crushed coquina for substrate?

[dyamazon]

I live in Florida and I can get crushed coquina for $1.79 a bag.

I realize it isn't "live", but would this work ok as a reef sand substitute?

Or would it pack down too hard for the sand sifting creatures?

[SeanT]

Isn't coquina mainly made up of pieces of shells?
I wouldn't use it due to the phophates in the shells.

jmo,
Sean