I've had a beautiful Betta in my 200 L tank for over a year now. The pet store told me he would not like the depth of the tank - but he seems to love it. They also told me the Betta would starve because the other fish would eat his food. I solved that by tossing flakes to the other end for the other fish and then dropping in his pellets one at a time right to him. He learned to come up to me to be fed very quickly. He peacefully shares his tank with several Gourami's, a Rainbow shark, Chinese Algae Eater, many tetras, and various other fish.
Betta's, particularly the males, are my wife's favorite fish, due to their fins, color, and personality, which can be very variable. Her first betta, Bruce Lee, lived in a 1 gal pickle jar with a little gravel in the bottom and a plastic plant that reached to the surface. We noticed when we added the plant that Bruce swam around a great deal more ever after, and he would frequently perch on fronds of the plant. (Incidentally, the curve of the pickle jar served to magnify bruce to majestic proportions.) I imagined my wife's prize pet a peaceful little fellow, until I caught a couple of tadpoles to add as temporary friends, so my wife could watch them metamorphose. To my horror, Bruce made a very gruesome meal of the first one I dropped in before I could do anything about it (I have kept large cichlids, and I don't think I have ever seen or heard anything quite so nasty as Bruce's live-feeding). Needless to say, the other pollywog made it safely back to the pond. Bruce eventually saw larger quarters than his original jar--a well planted 75 L communtiy tank. None of the other fish (gouramis and tetras) bothered him much. He staked out a territory in the upper folliage of some long-stemmmed bunch plants, where he would sit, his back almost exposed to the air. He chased any fish that accidentally happened into his "tree house", but otherwise shunned the open waters. I do not believe that bettas prefer close quarters per se, I think rather that it has something to do with their need to breathe air, and so requiring that the surface of the water be calm as their mouths are small. Everyone's bettas would thrive and feed better in tanks without turbulent filtration near the surface.
I have a red and azure young Siamese female that is doing very well in my community tank (moon and blue gouramis, white clouds, guppies, albino corys and a sailfin plecostemus). When I throw down pellets for her to eat I break them into tiny pieces - which she then picks up and balances on her mouth, swimming as hard as she can with it to a corner. It looks really sweet, but I don't know why exactly she does that. She also has a tendency to 'show off' when I observe her closely: she'll extend all her fins while facing me, and then bend her pretty tail to one side, so I can see it to it's best advantage. I noticed that on the other side of her tail she has a little bump, about 3mm in diameter - it looks like her muscle has over-developed like those of a weight lifter!
I find reading these comments very amusing, particularly Bruce Lee's story. I have 3 bettas in bowls at work and think they're beautiful, Their names are "Mars" (The bright red one) "Jupiter" (the cranky blue one) and "Random Task" (or Randy for short)(Austin Powers fans only) (the marble blue, red and silver one). Jupiter likes to flare at anything except Mars, who he teases by swimming leisurely past the point where the bowls meet and making poor little Mars go mad trying to show off and make him go away, then Jupiter turns aroung and away he goes again. I laugh at them frequently, especially at feeding time, Jupiter totally turns his nose up at anything except live worms, Randy jumps from the water to retrieve his worms, and Mars is so frantically swimming against the side of the bowl going "Me, me, what about me" that most of his worms are swept to the other side. I think I will always love these fish, it's a life addiction!
I have noticed that bettas are pretty easy to keep. I did a project on them and one of them jumped the fence into another male's area! The attacked male could have killed the other male, but he just hovered over the wounded. He wouldn't attack it even when provoked, and I was able to rescue the injured betta.
I have 4 Bettas, 2 males and 2 females, with the males being long-tailed. The longest surviving male (red) named Freddy had the honour of being the first fish in my 24-gallon (126 litres) tank. When I moved him from his 4-inch deep container (about 1/4 litre), man, he was lost with all that space! He loves to play with the current coming in from the filter. Will try to mix him with other fish, especially my 2 females. BTW, the other male is serving solitary time for failing to mate with my females.