jesatfis - I use the Aquarium Pharmaceticals (sp?) and haven't had an issue. Sometimes the color is between 2 shades, but as long as I know it is in an acceptable range I don't worry about it. I think to do reef you'd also want to test calcium and alkalinity. If I understand it correctlly, alkalinity is a measure of your tank's ability to maintain a constant pH reading. By that rational, if you maintain a constant alk you shouldn't really have to test for pH. Anyone have a different opinion?
SW_H2O - For FO or FOWLR you want to check temperature, salinity, pH, ammonia, nitrite, and nitrate.