Has anyone ever used one of these? [URL="http://www.marinedepot.com/ps_ViewItem.aspx?category=Hanna_Instruments_Checker_Colorimeter_Single_Item_Monitors_Controllers_for_Saltwater_Aquariums&vendor=Hanna_Instruments&idProduct=HN1181&IdCategory=FITEMOID&child=HN1183&tab=5&option1=Phosphate"]Hanna Instruments Checker Colorimeter Accessories[/URL] I am having algae problems even though my API test measures zero phosphates. This seems to be more acurate so I think I should invest in one. I'd just like to get some reviews before I spend the on the checker and the reagents.