While stationed on Okinawa the first time, I went into a pet shop to buy a toy for a friend's cat.  Next to the cash register was a blue-green betta like this one in about 1/2 inch of filthy water in a plastic cup.  I felt so sorry for him that I bought him, along with a small aquarium, gravel, a filter pump, plants, a fake rock for him to hide in, and a little catfish.  It turned out to be a very expensive cat toy! 

I went back to my barracks room and set up the aquarium.  After that, the sound of the water coming out of the filter really helped my sleep.  Having the barracks room to myself (it was a designated 3-person room), I had plenty of room, and other bettas needed homes.  I eventually wound up with 5 aquariums--3 small ones and 2 larger ones with more fish.  Each of them had a betta in residence.  Keeping them all clean and happy took up a good part of my off-duty time.

one day, when I went to feed everybody, I didn't see the original betta.  However, his rock hideout was big enough for him to be out of sight, and the plants had grown considerably.  I was sure I had just missed him.  I came back to the room for a late lunch and still didn't see him.  I had to siphon out his morning food because he hadn't eaten it.  I began looking for him in earnest.  I finally spotted him tangled in a dust bunny under the dresser.  When I reached under to pick up my now-dead fish, he jumped away from my hand.  I caught him and put him back in his tank, picking the dust off him as I did so.  He was fine.  He lived for the next hear and a half I was there, the year I spent back in language school, and was doing fine when I got back to Okinawa for my second tour.  I knew bettas could breathe air, but for more than 4 hours under my dresser was ridiculous.

Also, for anyone who has not had a betta, they can be very friendly, coming up to eat out of your hand and staying to be stroked.  Each one has his--or her--own individual personality.  That, combined with their striking beauty, makes them my favorite pet fish.  I don't have any fish now because of all the cats, but if you are looking to get a fish, might I suggest a betta?