In all this discussion I think we are missing the obvious. When a fish eats a certain amount of water is going to be ingested <duh> so if the water is rich in minerals each and everytime a fish eats its going to be getting extra minerals. I dont know about the extraction of air though the gills if maybe the water passing though there might present absorbtion options, I do admit a lack of knowledge here. Keny ------------------------------------------------------------------------- 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.