1fish2fish, I completely agree. Though in a way, when you adopt a dog from a no kill shelter, you are in a way rescuing a dog. You might argue that no, the dog you just adopted was not in need of being rescued, but in taking that dog out of the shelter they can go and rescue another dog that is at a kill shelter. In fact, one of our dogs was rescued from a kill shelter, we just happened to adopt him from a no kill shelter. But in adopting him they were then able to go and get another dog from the kill shelter. I would say that it was a win-win-win!
We got a great dog, the dog got a great home (he is now 10-12 years old and still young!), and the shelter can help another dog (even though this was 8 years ago...).
But since there simply are not that many rescues for bettas, I try to buy from the places that keep their fish the best. My rational for this is yes, I can buy ONE fish in horrible conditions. But then I just gave them a profit and an excuse to keep all the rest in horrible conditions because someone else just like me will come along and do the same. Instead, if I choose not to buy the poor fish kept in horrible conditions, and if no one else did either, they will literally start just throwing money away. They had to buy the fish in the first place, if it doesn't get sold they lose money. Eventually they will lose enough money that it won't be worth them selling them any more. When I go and buy a fish kept in healthier conditions, displayed nicely, etc, and pay top dollar for that fish, the person/company/etc that sells them will have incentive to keep their fish healthier because they get the most profit. I have no problem paying $14 for a fish at my local Petco because they actually do a really good job of taking care of them and take pride in keeping them looking amazing (and it is torture going in and looking at them when I can't get any more. :'( ). Yes, one fish really appreciates being "rescued", but all of the others that don't get rescued and have to sit and die in those little cups don't appreciate it.
What I would strongly recommend is filling out a comment card or writing the store. Tell them you simply could not buy fish from them because you were appalled by their conditions. Go on to a site like Yelp and write about the sub-par conditions of their animals. Dropping profits is the only thing that will get their attention.