You can find it on GARF's website.
I personally didn't have any luck with aragacrete. You gotta cure it for 6 months with constant daily water changes. A lot of people were able to make aragacrete plugs and put them in their toilet tanks for daily water changes... but it still takes a while to get it going.
You could look up that thread with the pond foam and bits of live rock. It would be more instant and you wouldn't have to deal with the pH ever climbing up too high.