@ TheBrit,
I respectfully disagree with you.
Natural nippy and aggression problem can't really be solved by having plants. I have been there. My aquarium is very heavily planted. The aggression problem wasn't gone just because there were hiding places. Some fish got injured over it and I had to transfer some of them to different fish tanks to avoid more serious problems.
Just because someone was able to keep a few betta fish in community tanks, it doesn't mean a thing. There were zoos kept dogs in lions' pit. Can it be done? Yes. Is it recommended? Hell NO!
Betta in a community tank is a time bomb. There isn't any problem until there is a problem. To avoid unnecessary injury or even death for your fish, it is not recommended at all to keep a betta in a tank full of other fish... especially not with the nippy ones like Tetra.