Drs Foster and Smith is the place to buy it from. Whenever I purchase buckets, I go through them. Although, I'll need to talk to Elmer's about the statement above. If that's true, I'll probably start buying from them.
You'll get a nice little Magnesium boost as well. The Coralife Has high Ca & Mag, but a lower Alk... Instant Ocean has a high Alk, but lower Ca & Mag levels.
<table align=center><tr><td valign=top></td><td valign=top><p align=center style='text-align:center'>Calcium   </p></td><td valign=top><p align=center style='text-align:center'>Alkalinity   </p></td><td valign=top><p align=center style='text-align:center'>Magnesium</p></td></tr> <tr ><td valign=top ><p >CoraLife</p></td><td valign=top ><p>   560</p></td><td valign=top sp 9><p>   9</p></td><td valign=top ><p>   1380</p></td></tr> <tr><td valign=top ><p></p></td></tr> <tr><td valign=top ><p>Instant Ocean   </p></td><td valign=top ><p>   350</p></td><td valign=top ><p >   12</p></td><td valign=top ><p>   1070</p></td></tr> <tr><td valign=top ></p></td></tr> </table>
I got some pretty nice results when I combined them. I actually purchased both from Petsmart, and had a few coupons which helped. Otherwise it would have been a little more expensive, but I was able to get my hands on it that day.
(I only picked up the 50lb mix bags for the first experiment though)