Was this a chain store or a mom and pop store? I'd stay away from the chain stores unless your just trying to save a few bucks on supplies and such and find a mom and pop you can trust for you fishes/corals..etc.
Petsmart/petco employees are mostly just people hired off the streets and have no more knowledge (and some less) than you or I or anyone who spends enough time in forums like these and educates themselves. I started my first SW tank back in October and have been in here almost daily from the beginning. It took me about a month to realize how clueless the people at the chain stores were and I never went to them for advice.
If you can find 2 or 3 lfs that are in business for themselves, you will hopefully find some you can trust and will help you out. I have 3 differant stores I frequent. All will give varying answers or opinions on things that I ask (just like in a forum). I use what I've learned to try and make an educated guess on which direction I go.
As an example, I asked all 3 lfs employees/owners the same question about target or broadcast feeding for my corals. LFS#1 said n"no need, don't do it. You'll just have problems with water issues from excess nutrients and have phospahte issues." LFS#2 said "do it. Your corals need the food to grow. Use these products". LFS#3 said "do it" but gave a differant list of producsts to use. I settled on a combo of #'s 2 and 3. I picked the combo of foods I thought would benefit my system the best.
I now use a combo of frozen mysis, reef gourmet and formula two. I mix a drop of garlic extreme (every other day), a drop of vit chem, about 8-10 drops of zooplanktos-s with some tank water and the other ingrediants and pour it back in the tank. I target feed some of my corals frozen table shrimp 1-2 times a week. So far no issues.
I know this was a bit longwinded but just wanted to hopefully encourage you to get away from the chains and get to a local lfs.