HC GFO. How much does one pound amount to.

[rhody605]

How much volume does one pound of hc gfo amount to? How much do you use for say a. Medium stocked 80g tank. How often to change it?

Is it light like carbon?

The reason I ask is I want to add it to my system and don't know how much to order. Most places I find sell it in 1 pound cases. For around $25 per pound. Depending on order amount of course.

Thanks for any info.