If I remember correctly, white cloud minnows are fairly active schooling fish...so they need some room to move around. They might stress out in a 2-gallon, but I'm not sure (they are hardy fish, from what I hear). Also, they like cooler temps, if I'm not mistaken. I bet they do fine at higher temperatures, as well...but then again, I don't have any first-hand experience.
Don't forget that they school, so I think you need at least 4 in a tank. With a 2 gallon, I don't think you could comfortably fit much else...
Disclaimer: I'm a newbie--so make sure you double-check everything I say.
- mb