You know, what it really all boils down to is the people that Petco hires at the various locations. In our area, we have access to several LFS that range from 1) tell you anything to get you to buy something, to 2) really work with you and help you build something that will be a healthy habitat for your aquatics. Petco.... I honestly called the Petco customer service line about one of our local Petco's and described how poorly the marine fish were being taken care of......amazingly enough, they now have a new saltwater manager and the tanks are run by a really nice kid (I call a lot of people "kid" - I'm old)

who is clearly knowledgeable and cares about his charges. We've ended up buying really underpriced scooter blennys and just a week ago, a dwarf zebra who is just beautiful and acclimating to his/her new home well.
There's good and bad everywhere. As the person buying - it's our responsibility to research and make good decisions and if needed, point out something going south and/or bad advice from a Petco or
even a LFS store employee.