I have opened our pool and it had a lot of algea growing it in. The pool is 27,000gals vinyl. I added an initial dose of 20 gals of 12.5% Liq chlorine which figures out to roughly 90 PPM and this AM I tested with the OTO test kit and a zero reading of cholrine (clear no color at all) So we put in another 12 gals which should be roughly 54 PPM and again I have a zero reading on the OTO test kit. (clear no color at all). I have never put in this much chlorine before and I just wanted to make sure that there is no way I have put in too much chlorine that its fooled the OTO test kit.