My Betta didn't like them. Flared a buttload. I figured it was just because he was new and the minnows were already in there, and it was a planted tank.
None died but the morning after he had tears in his fins probably from chasing them or bein stressed. I took them out and fed them to my catfish, who ate them. Yeah, so depends on how well planted it is and how chill your Betta is. If when you walk by and he flares, probably not a good idea. Or if he's just super mello and doesn't care... Go for it :B