its been done before...keeping a betta in something like that...but that doesn't mean it would be a very healthy betta....I wouldnt get anything less then a gallon for a betta...that's only around 3.6 liters which doesn't add up to be 1 gallon close but not quite... point being it'll work...just wouldnt be tha best for ur betta...
Not cool! First of all, Bettas are TROPICAL FISH. They need heat, filtration, and aeration as well as a good amount of swimming room. The 6.7 gallon may have room but how cool would it look with electrical wires for a heater and filter hanging out of it, and that is what you would need (at the least) if you want a healthy, happy fish. If all you want is a wall decoration, it a cruel thing to do to a fish. I think it also needs to be said that Bettas are top swimmers. They need to come to the surface to breathe through their labyrinth organ (much like us, a Betta can breathe air as well as through their gills - in fact they HAVE to). This means they need something with a good surface area for them to come up to. Those look like the surface is very small and enclosed inside an even smaller hole in the "Bubble". It may cause a problem for the air exchange for your fish. It more than likely sounds like I am the biggest "party pooper" on this forum sometimes, but seriously there is so much just plain wrong information going around about Bettas and I have become so tired of it, I just open up my mouth and say what I think. I also have a lot of reading, studying, and watching Bettas behavior, talking to people who have bred Bettas, treated Bettas, and loved Bettas to rely on. Anyone wanting any sources for the information I give let me know and I will gladly share with you. There is also an excellent forum devoted especially to bettas. I am not being disloyal to Fishlore.com, but I feel if one is going to own a fish and do well by it you should take advantage of ALL the help and information you can get. The site is and there are some folks there who know Bettas much, much better than I do. (They also have some BEAUTIFUL pictures that are worth the visit by themselves.)
Please learn about the Betta before you consign him to a bowl. (this is addressed to the public in general, if the shoe fits ...) :