There are 3 Petcos in Metro Detroit that sell saltwater. 2 are absolute crap, and I totally agree with you that those locations need to stop torturing (selling) livestock.
The 3rd location is amazing! I've talked to the guy that runs that Fish section, and he is very knowledgeable. His livestock all seem to be doing well, and the tanks are very clean.
I think Petco's problem is - they don't always have knowledgeable staff. They just hire someone at min wage, hand them a list of chores that needs to be done everyday, and put them in charge of it. Without the proper knowledge, they won't succeed. Apparently, on occasion though, they do employ someone with knowledge, and who cares, and the section thrives.
Along these same lines, there are some LFSs that should also get out of the business. I've walked into a couple of LFSs in Metro Detroit, turned around and left before getting 5 feet into the store. Brown slimy tanks, and the stench that accompanies it, is the sure sign of a poorly run store. But when I do find a great LFS, with great livestock and knowledgeable staff, it's worth the drive to go there, no matter how far away it is!