crushed coral vs sand

[mikealb]

I have had my tank 4 years now. Its FO, 90 gallon,with crushed coral. A local aquarium staf suggested I replace the crushed coral with sand. Also, another staffer said the crushed coral loses its buffering power. The tank was just moved and all the crushed coral rinsed thoroughly with hot water and replaced. Do I need to replace this. Should I use sand, if sand what type. I rmemeber seeing on this or another board you can buy the sand in Home Depot.
Thanks in advance