Yea do not listen 100% to what your LFS
says, they are in the business to sell whatever they have. Heed their warnings though for sure because if they warn you for example "that mandarin will only eat live pods
" listen, because when they give advice that could ruin a sale they are most likely sincere.
If you see a fish you like and they say "yea, it's 100% peaceful, won't eat those little gobies" research it first and see if they're truthful. It's best to know what you want to buy before you get to the LFS
so you can research it, unless you have a smart phone in which case you can research on the spot.