How about crushed coral? That is what I was taught to use by June O. I put one cup of it in a nylon stocking or whatever in my filter, esp. when the CO2 is running. The snail's shells have improved immensely. Rumor has it that there may be two 40lb bags of it at the meeting next month. Susan _______________________________________________ GSAS-Member mailing list GSAS-Member@thekrib.com http://lists.thekrib.com/mailman/listinfo/gsas-member