Update if you're intersted: one of the GloFish apparently starved to death despite getting plenty of food (I guess it just didn't come up to get any ): I isolated it and sprinkled some food on top of the water but when I came back a while after it was dead. Oh welll.), so I went and got a Tiger Platy and a Chinese Algae Eater. They all get along nicely, though Milo sometimes chases after the Platy, but gives up after a few seconds, almost like he's just kidding.
Six Gallon Tank
Milo - CT Betta (M).
Mulder and Scully - Red GloFish. (/dork)
Tony - Chinese Algae Eater.