I will say this... I like to see the positive in people. Since this LFS has given him deals in the past and was willing to take it back, I bet the LFS might just not be as educated on it as we would all hope. LFS have a lot of animals (fresh and salt), gear, corals, meds, and sometimes reptiles so that is a ton of information to know.
Ideally they would know more about what they are selling, but just the other day I was at a LFS buying some supplies that
@Humblefish recommended for my situation and the owner told me that those products would not be good for my scenario. This LFS is really good and is really knowledgable, but just was wrong in that situation. I think this may just be a case of the store not knowing the product.
Just my super positive two cents.