I've been using it for 6 years or so in a DIY reactor with my ATO primarily as a pH booster as I also use a Ca Reactor. On its own it wouldn't meet my Calcium Carbonate needs but it does have its benefits and its inexpensive and easy to use this way. There is nothing I can say about it that isn't covered thouroughly in this article:
What your grandmother never told you about Lime by Randy Holmes Farley:
http://reefkeeping.com/issues/2005-01/rhf/index.php
