I don't believe this is totaly true because a betta feels as he has to "patrol" the tank and if he was in a 55g he would get tired really fast and get stressed out because of there long fins and eventually they would die or get sick from the stress also if there are other fish that like to eat the food really fast the betta wouldn't get much because I've heard that like to look at the food for a second to make sure its really food before they eat it and by that time the other fish would have eaten it. Also like arrowhead said the current would be to strong for a betta
I disagree with this. I think it depends more on the individual fish or combination of fish in the tank, plants and decor, filtration level, etc as to whether or not it will work out with a betta. A very timid and shy betta would probably do very poorly in a large tank, especially one without much plants or cover. A very aggressive betta would probably do somewhat poorly in a large or heavily stocked tank as he would spend all of his time chasing the other fish. A middle of the road betta and appropriate fishy friends would probably do just fine, regardless of the tank size.
As an example...I had set up a 10 gallon tank for some zebra danios and cories. Just for kicks, I threw in a nice red VT male that I had, before I had bought any of the community fish. He did nothing but hide behind the filter for days and hid until I finally put him back in his 1 gallon. He is fine and happy in the 1 gallon tank.
In this same (now empty again) 10 gallon, I added this burgundy/blue VT male that I have. He was thrilled and would hide in the big fake rock and then spend his days swimming through the plants. I eventually moved him to a 25 gallon planted tank with a few Otos (algea eaters) and a bunch of ghost shrimp. He isn't "stressed" by the size of the tank at all. He swims and swims and then rests on the leaves of the plants or on the driftwood when he is tired. He is pretty aggressive and will chase the Algea Eaters if they are in front of him. But they swim off and he goes back to minding his own business. I don't dare add any regular fish to the tank because of his big attitude. But the size of the tank doesn't bother him. He seems really happy. I even have a regular biowheel power filter in there and he seems to like swimming in the current.
As a third example, by this time the 10 gallon had little cherry barbs and dwarf platies added to it. So I added a very docile dark blue VT male that I had to it. He got along GREAT with the little fish (after a day or two of working through his issues) and would swim and eat right next to them. He seemed to like swimming around the tank and in the current from the sponge filter/bubbler thing. However that tank was FULL of plants those first few days to give everybody lots of hiding spaces.
So it all depends on the betta. That 10 gallon tank sprung a leak this week and was emptied and mr docile blue betta was put back into a gallon bowl. And he is just happy as can be in there too.
So the moral of this LONG story is that it depends on the betta and the tank and the other fish. Bettas don't require a small tank. But because of their aggression they are often kept that way and often for good reason. I didn't mention up above my other blue/white butterfly VT male who is so nasty that he will lunge out of the water to try to get at me (and not in a nice 'feed me' way either) and bashes himself into the tank if he can even see another fish. He will never ever be put in with anything, not even a little shrimp. He probably would stress himself out if put with other fish (and he would kill them or at least chase them mercilessly).
If you have the space, appropriate community fish and lots of plants/hiding places...and a nice-ish betta...doesn't hurt to give it a try. Just be prepared with a net and the trusty bowl if things go wrong
(sorry! I'm a blabbermouth tonight)
All so sweet and amazing all this nice stuff about bettas, i can't wait to go on thru the years and learn more and experianced like you guys 
i just need to let my bank account heal a bit 
So a 10g tank kit sounds good, or the 5g, but what kind of fliteration would be recommended to use? a little undergravel filter with a tube with the bubble stone thing? 
I have no clue! and i do need to cycle the tank of course right? and what are the recommended water changes? Well any advice would be great! Thanks!
