I tested Alk in my tank with 2 API test kits, One was brand new, never before used and the other I have used for months and it has worked fine. No matter how many drops of solution I add to the test tube it will NOT turn blue. I added 30 drops and it was still yellow! I immediately went and tested my 20G and the same thing happened. I tested my tap water and after about 4 drops it turned blue. Ph (8.3) and cal (440 ppm) in my 29G seem fine.\n\nAbout a year ago the same thing happened but after a couple days I re-tested with [I]the same test kit [/I]and then the test accurately measured my alk. \n\nThe only thing in common the two tanks have is that recently I added a lot of baking soda to both tanks -\-perhaps too much but not an insane amount. I also added calcium to both tanks but Kent cal to the 20G and SeaLab #28 into my 29G.\n\nCould too much baking soda affect the API alk test?