Came across all the posts on the CYA black dot test and the variance given by the Taylor 50ppm standard solution. See that it isn't being sold anymore on TFTestkits. Actually can't find it in small quantity (less than 16oz) anywhere. Have no CYA test reading experience so nothing to compare to and I doubt my readings on every test. Waist high, sun to my back, etc. if all fine but if I don't know what it should look like then....?? Some say completely gone, others say you can barely see the edges, etc. Is my only option to just go ahead and order the 50ppm solution and use it to train my eye? Learn what 50ppm looks like and go from there? Probably 14 ounces more than I will ever need.