I suggest you mention to them next time you're there that they are losing serious business by stocking beta hexes in an environment like this. Tell them you have many friends who are aquarists and they all believe that this is outright cruel and wont purchase anything from HFF for this very reason. Just because they say that betta hexes can tolerate water with a low oxygen content and confined space, it doesnt mean they want too.
I dont think I will ever bother buying from HFF again. There is nothing that pisses me off more than cruelty to animals - especially for human pleasure or profit.
Check this out. A dual tank so they can look at each other and flare their bodies and enhance their colours. They dont call them siamese fighting fish for nothing - no bloody wonder in a tank like this, simply made for human pleasure, but of the wrong sort...
http://www.ask-the-vet.com/cgi-bin/goto.pl?service.bfast.com/bfast/click?bfmid=5327311&siteid=40583291&bfpid=53463&bfmtype=hardgoods
oh, and breakaway - even if you can, DONT keep 2 betta's in your large tank or you'll be taking out a dead one the next morning!