Is you LFS testing for ALK, calcuim, salinity. ph, on top of the amonia, nitrates, and nitrites. If you are having trouble keeping snails, then your salinity is probley off.
As suggested before, don't trust your LFS 100%. They are in business to make money, your money. and too many don't care how they do it. There are more people on this site and other sites that have been burned by a LFS when they were new to the hobby. So many people were told you can keep this with that no problem. and after research they find it just isn't so. One thing to keep in mind, the LFS make money off of you, and a lot of it. We here on this board do not make a nickle off of you. We have nothing to gain by telling you wrong info. We are here simply because we love this hobby, and we love our tanks, and we want to help any one who has a question. So think about that, and if you want to trust your LFS over us. then so be it. But trust me, we could tell you alot of stories about LFS giving misinformation just to make a sell. Not all stores are like this, but they are rare.