I think the tubifex should be fed about once a week, since they're a very rich kind of food. What form do they come in, freeze dried?
I feed my corys three pellets a day, at different intervals, and I have four of the beasts. They seem to be doing well enough on that. Now and then I float a few fish flakes in the water and they eat those as well. I haven't tried the worms yet but I'm going to get some next week. The thing is, normally with corys you might have them in a community tank with livebearers or tetras or whatnot, and they get a decent diet scavenging what the other fish don't eat as well as having a pellet or two per day, but with a
betta it's more difficult because you make sure you only feed the betta as much as he's guaranteed to eat and digest.