Twice a day, once either in the early afternoon when I come home from work or the early morning, then once at night at around 10:30pm. Normally my auto-feeder would facilitate his eats but he's not in my main tank for the time being, I have quarantined him for the last week or so due to some spots showing up. They have disappeared from his body, and none have returned so I think it may be time to put him back in the main tank.
Also, a fat Betta is a healthy Betta. My fan-tail has a pretty big gut from all the bloodworms and crumbles I'm feeding him. I do it portion by portion, just so not to pollute his home. If yours is pooing a lot, just keep up with the water changes. 8)