I think it's both people involveds fault, All my LFS and chain pet stores around me have the signs they all say "common pleco" and all say 20+ inches for adult size. Yes they should carry the smaller plecos, but how many people when offered a "dwarf" sized pleco would say "well, the bigger one will eat more algea". If you own a pet any kind you should take the time to read on the species or breed of whatever kind of animal you are taking care of. The problem occurs when someone is just disconcerned and comes in and says I need 2 algea eaters. The store employee more than likely is not going to say "how big is your tank, or do you know that this fish will get....".