I'm curious to know what types of fish you've had with your betta.
I had a 10 gallon tank, and all together for the longest time I had two Bleeding Heart Tetras, 1 male guppy (he was tiny), 2 algae eaters, and a crowntail betta. And they all got along, none of them had fights.
Alittle later I had a goldfish, a molly, and a cory catfish added to it, and they fit in fine.
My betta had also been with an angelfish, neon tetras, and a red-tailed shark at one point, this was for a short while. Dearing the time I learned he did NOT like dwarf gouramis, at all.
So, what kinds of fish have you had with bettas?