I accidentally might have stunted the growth of a fry in a 5 Gallon!! I would not do less than a 10 gallon with them. Also you need to add to your school/shoal, the min. number of these guys is at least 6 -12. The more you have the better they show themselves. Try adding a Dither fish, I use Neon Tetras (little pigs!). Also try adding floating plants, they don't like harsh light.