I've got two male tanks, one for rares and one for common.
She likes common Veils and they seem to get along well with lots so when I realized how lonely Emo was I added some neon tetras and slowly the population grew. I've about 22 fish in that ten now with Goat; neon, glow lights, black neon, cardinal, roberti bloodfin/green fire fry, one double-albino neon and one albino black neon.
The double albino neon has no red marking and is just a pink thing with blue eye rim and blue line.
The albino black neon acts more like a pristella... so owns the top half of the tank when the ruling heavyweight is sleeping.
That's the ten, I keep a five with five or six pristella (gold and regular) in with my specialty tails whenever I get them, right now its Sherbert a half-moon. When he's angry he tries for 3/4 moon tho, been to 215° a couple times!
My sorority tank I have one male fancy gupper with a harem to keep him off the betta, a pair of male molly (survivors of the molly death feast of 2010) and one chinese algae eater.
The algae eater is getting a bit long in the proboscis, I may have to take him back and get another young one, but he sure does keep the tank clear. They attack using super-hickey power but are incredibly tough. If he was alone with a male betta I'd bet on the algae eater but the one time he really went at a girl (she deserved it) three others jumped him and he held himself out of the water for about 30 seconds. They can jump to clear small waterfalls.
From what I've seen most betta like company as long as they aren't crowded, Goat likes to swim through the feeding cloud of tetra to share in the fun on the little fancy guppy pellets.