I used to have Tony in a 2g Hex. I didn't buy it, I got the tank and the light fixture used free from a friend.
The light is a great life, capable of growing a variety of plants if the correct bulb is used. I used a Tetra Whisper 1-3g filter. Had some anacharis in there, as well as some hornwort. It all worked fine (until I got cynobacteria in the tank, and I was too lazy to get rid of it so I moved Tony to a divided 10g).
My sister had the 1g "tank". I think it comes with an undergravel filter, at least my sister's did. She wasn't very good at keeping up with water changes, though, so I can't really share any success story there (she has never lost a betta in that tank).