Just to tag along...I've also been looking for a "cheap" alternative to buying argonite/oolite/etc at LFS for $1 per pound. Unfortunately, I haven't found anything around Andrews AFB that isn't silica based. As for dry rock...Bulk Reef Supply (my personal choice) runs out of stock fairly fast but you can also try www.marcorocks.com. They seem to have good products at decent prices. Good luck with the tank and be sure to post pics of your progress!!