I dont have any tank mates for my Betta's but two of my friends do.
Betta + 5 panda Corydora's in a 10G tank.
Betta + 4 Panda Corydora's in a 5-7G tank.
In the first case there was no problem. In the secodn case the Halfmoon who used to share the tank with the Panda's was replaced by a Super Delta since the Halfmoon would even eat the Panda's sinking tablets. Seeing a halfmoon with a sinking tablet in his mouth is kind of funny the first few times, but it does become a problem later when you have to keep him away in order to feed the cory's.