I have to respond to the above remark that one may keep one male with many females in a community tank. While often aquarists face different sitautions and circumstances which create different reactions in the fish, I feel it important to mention that sometimes (frequently according to one local Betta enthusiast) a male Betta will select a single mate or a small heram (2 or 3 females) from those you provide for him. He will then kill off the "rejects". Also, I will ditto the above remark about the male Betta becoming agressive toward similar species. The red-tailed sharks and Siamese & Chinese algea eaters being the most common. It often depends on the size of tank on how agressive any species can become. The smaller the tank, the more agressive as a general rule.
I tried keeping a male betta in my 20 gallon community tank with corydoras cats and White Cloud Mountain Minnows. Everything was fine until I noticed that one of my minnows had a couple of bites in its back. Doubting that either the other minnows or corys had gone on a rampage, I removed the betta. Speaking with experienced tropical fish dealers has told me that it is likely the Minnow did not recognize the betta's display, and didn't get away from it quickly enough. The betta is now back, quite happily, in his two-gallon bowl, and there have been no further incidents in the community tank.
I have a beautiful betta, named Obi. He lives in A two gallon tank in my dorm room. He is gorgeous with a purple body and red fins that have an iridecsent blue at the base. I have had many bettas in the past that have all done very well in community tanks. I put in a bottom feeder fish because his tank needed something to clean it, and at first I thought that he might not accept it, as he has been very aggressive towards everything (including things that I could not seem to see). So far they have done swimmingly (LOL) and the tank looks better than ever.
Any betta I have ever kept has much rather resided in a small bowl without a filter or air pump than a larger tank. If placed in a large community tank with moving water due to a filter, my bettas seem very lethargic and will not eat. Even in a small 2 gallon tank, they always manage to squeeze themselves into a pile of large rocks on the bottom. The natural habitat of bettas is weed-choked and shallow, so by nature they prefer small, enclosed spaces.
I have 6 male bettas, my pride and joy being Worf, my large blue and red and the dad of the first spawn of fish I ever raised. My favorite betta (and fish) of all time was Jadzia, Worf's wife. She was so puny and dull when I bought her but in her bowl she just blossomed! She was a gorgeous and radiant red-blue-green colour! When I moved her in with her juvenile daughters, in my 22 gal, she paled and had her fear stripes most of the time, like the others (I think they're always on guard around each other) But I made sure the kids were treating her alright (and vise-versa). She did fine for a while but then she started looking really weathered (by this time most of the girls were gone). Later on she moved to my 68gal, then my 10gal but her health was going down hill. I tried medications but to no avail. It was very sad when she died. Both her and Worf definitely seem to have done better in their bowls than in the tanks, although they have some sons who seem to be doing fine with the tank life (different tanks of course) I think bettas find security in smaller quarters. The colours of the females are definatly nicer in bowls! If I could only have one fish, it would be a little puny female betta in a 1-2 gal bowl so I could watch her turn into a little gem like Jadz did :>
I, too, have experience with male and female betta. I have one male in a 29 gallon tank with 2 dwarf frogs and 2 shubunkin goldfish. Mr. Roustabout (the betta) does just fine with his roomies. Actually, I worry more about my frogs getting his tail, than the other way around. My frogs grab hold of Rousty's tail and go for a ride when he's trying to show his aggressive behavior! It doesn't happen very often though. I had three females in the 29 gallon tank with the male, but they ganged up on him. They now share a 10 gallon tank limited to girl betta's only!