I wanted to add a followup to Shango's helpful message about the Estimative Index fertilizing method. In my reading I saw that adding magnesium via epsom salts is recommeded if you have very soft water. We do here, maybe not that soft... but I certainly have soft water because I am using RO/DI water. Per Barr's article <http://www.abaquaria.com/forum/showthread.php?t=2>, MgSO4 should be added once a week, to 7 ppm. The solution is described as-- Magnesium Sulphate - 70g to 500ml of water and add 50ml once a week per 100L of water If my math is right that is 7 grams per approx. 26 gal, once a week... which would be more than 21 g in my 90 gal tank depending on true water volume. That seemed like a lot until I remembered that epsom salts are actually a hydrated compound, with 7 H2O for each MgSO4. More than half the weight of a given amount of epsom salts is actually water, so it's not as much as it looks like. Still, with this method the water changes will be very important. All I need to pick up is the potassium phosphate. Hopefully one of the many hydroponics places in the Fremont area will have some so I don't have to go all the way to Burien. MS _______________________________________________ GSAS-Member mailing list GSAS-Member@thekrib.com http://lists.thekrib.com/mailman/listinfo/gsas-member