Personally... I think API is a great value for the basics like ph, ammonia, nitrites, and even nitrates if you're not picky about detecting small levels of it. Regarding the ammonia in your new water, as dskidmore suggested, it could just be as simple as a bad or expired test kit. It happens from time to time on all the brands. Or it could be that the LFS
's water is not as pristine as they think. That's why I'm hesitant on buying water from a LFS
- I can't control the process. Doing it at home, I'm 100% in control... good or bad! Maybe you can take the sample in to some other fish store and have them test it, and watch to see the actual values.