Don't buy him, that'll just encourage the shop. Steal him instead
If the manager gives you any shit, you could email him this and also remind him that fish are covered under the 2006 Animal Welfare Act (they weren't covered previously and some people think they still aren't) and he has a legal duty to provide-
* somewhere suitable to live (ie not a fricking vase)
* a proper diet, including fresh water
* the ability to express normal behaviour (debatable whether a fish can do this in an unfurnished vase with no hiding places)
* for any need to be housed with, or apart from, other animals
* protection from, and treatment of, illness and injury. (fish will be exposed to ammonia in an unfiltered tank. Also, lower temperatures in an unheated tank mean that bettas- especially the long-finned ones- are more susceptible to fin rot.)
He might give it the old 'bettas live in puddles in the wild', which is total bollocks. They can survive in puddles in the dry season, they have an organ which allows them to breath air from the surface, but they live and breed in streams, ditches and rice paddies. Ask him if he's seen a rice paddy. They're massive.
If all else fails, complain loudly in the shop in front of other customers. I've done this before and been thrown out, but it made me feel better.
Sorry for swearing and sarcasm, been kept awake all night by demon toddler.
So, Got my reply - shop owner says he was ordered by a customer who then changed their mind.
Shop has no spare tank running ( this is true, they only have a tiny fish bit and there is not a suitable space) Owner says he is going to set up proper environment and that the vase is only temporary.
So, I will be observing the situation this week! Will update..
Dd has been reading this over my shoulder (she is a keen fish rights activist) and she agrees with the stealing him idea but hopefully it doesn't come to that.
Hopefully demon toddler has a good night tonight Eau.