Bob, Many thanks for the water chemistry lesson. I have an inherant inability to grasp some of the science. Your "layman's" explanation helped. Kevin Korotev Milwaukee, WI USA ------------------------------------------------------------------------- This is the apistogramma mailing list, apisto@listbox.com. For instructions on how to subscribe or unsubscribe or get help, email apisto-request@listbox.com. Search http://altavista.digital.com for "Apistogramma Mailing List Archives"!