I made a large error in my last post on gravel containing shells: Where I wrote ppm when measuring KH and GH, I of course meant degrees hardness (dH). Sorry about that. Please note new email address: Roxanne Bittman, Botanist Natural Diversity Database CA Dept. of Fish and Game 1220 S Street Sacramento, CA 95814 Phone: (916) 323-8970 Fax: (916) 324-0475 Internet: rbittman at hq_dfg.ca.gov