changing out crushed coral

[Nihoa]

hows this for a mess: our tank was bought already established and had only 2 ocellaris clowns in it and about 40 pounds of crushed coral. great filter but rarely cleaned, no clean up crew, no skimmer, not much of anything but a few fake plants. we looked at it as a fixer-upper and had no idea the problems that were going to be associated with trying to turn this tank around.

one big problem is that there is 2 years of crud settled down into the crushed coral that clouds the water everytime its disturbed and that spikes our ammonia like crazy. i want to switch out the crushed coral for sand and wonder how i go about doing this.

we now have 40ish pounds of live rock in the tank which has been in there at least a month. if i pull the water out and the liverock, put it and all my inverts & fish in a bucket, can i dump the crushed coral and replace it with plain aragonite? not livesand but plain sand?