All the advice given here is great and it is given by knowledgeable people with nothing to gain.
On the other hand:
1. Pet store employees are there to sell fish and make profits for the company and commissions for themselves (a PetSmart employee told me there is *no* need to cycle a tank before adding fish....hogwash!).
2. Pet store employees can't be expected to be knowledgeable in all areas...after all, they have to sell fish, puppies, kittens, birds, reptiles and all their supplies. They are, as the saying goes, often "Jacks of all trades; masters of none."
3. If you have a local fish store (LFS), you may pay more but you're paying for knowledge; they love fish and don't want to see them going to conditions where they won't thrive
4. Shrimp do not tolerate changing conditions so only put them in an established/cycled/stable aquarium (I learned this one firsthand after killing 12 in a cycling tank).
5. Shrimp are sensitive to copper so you can't use any plant fertilizers, medications or supplements with copper.
6. Some shrimp species need acidic and some need alkaline; some need cooler temps and some warmer. They are like all fish in that they are all different.
7. Listen to the people who have actual experience; thank those who don't as you walk out the door.
PS: I have worked in both pet stores and LFS and I know of what I speak.