I wouldn't necessarily throw a blanket statement out, and there are plenty of good ones, but indeed fishstore advice should be taken with a . . . wait for it . . . grain of salt.
While I'm hardly experienced enough to really know a heck of a lot, I have learned to simply take their advice "Under consideration." Even though the owners and usually the employees are enthusiasts in the hobby, it is a business after all and if they don't move their products, they won't be in business for long.
We have two dedicated fish stores (And a general pet shop that actually has a nice fish department run by a couple of seemingly pretty on-the-ball fellows) and even I, based on what I've learned here and other reseach, can see that they're not always giving out the most sound advice. Of the two dedicated shops, one told us to go with the cycle-by-damsel approach, the other said to use Bio-Spira and we could start adding fish the next day.
Sometimes it's simply a case of the "That's how I've done it for 20 years" syndrome, sometimes ignorance, sometimes an effort to make a sale.
I've also already noticed an interesting dynamic . . . and that's the relationship between the independently educated buyer and the people running the store and I keep that in mind whenever I'm in a local shop. The owners/employees undoubtedly consider themselves the "experts", and probably consider most customers ignorant and in need of education. It's only human nature that a self-considered expert might bristle and be less cooperative when somebody they consider uninformed contradicts them with "by the book" statements, not the knowledge of the ages they themselves have earned through their hard labors . . . like "Hey, I've been doing this for years and if this dork doesn't want my advice, fine with me, let them struggle without the help I'm giving them." Thus, whenever I get advice at a local shop that goes in complete opposite of what I've learned elsewhere (in several books and here), I usually just nod and say something like "Oh, okay, thanks." Seems like you get better and more in-depth information if you appear to be receptive to it . . . to a degree. I've had to coach my wife in this, the other day we were in a local shop picking up some chromis and she commented that they were going into our QT. The store employee said (Something to the effect of) "Oh, you don't need to quarantine them, you could put them right in your tank." Then my wife responded with, "But that's not what our book says." I sensed a bit of resentment from the employee and afterwards told her about the nodding-acknowledge-thank you technique.
One other factor is that it's probably just the owner/operator whos really the resident expert. Seems like most employees tend to be younger and undoubtedly less experienced and more likely to hand out misinformation, although I'm not sure it's always intentional. Just last night we were in the store again checking for small clowns and we asked about a couple they had and the young man actually admitted he really didn't know too much, and then went and asked the owner for more information.
