I got 5 of them for $5 at petco lol. They are about $1.50 each, very hardy too. They eat my betta flakes (the reason I went back to the flakes was cause they eat whatever he misses). They will also eat a whole hikari betta pellet, and bloodworms. They eat lots of stuff.
They are pretty entertaining too, I have 1 male and 3 females. Females are kinda red like a serpae tetra, while males are silvery with the phantom eye on the side. They do a sort of courtship thing too between the male and a female, or if you have 2-3 males they will sort of "play fight" I have heard, and try to win over the females lol. They get about 1.25 - 1.50"