I have a peculiar question. I have noticed that my Rummynose Tetras appear to change color- they get pale when the lights are off! In the daytime, all of the small school of ten that I have show bright red noses and vivid markings on their tails. However, if the light has been off for more than about an hour, I have found that they show no red at all, and the tail markings are very indistinct. Has anyone else ever noticed this? Does anyone know what may cause this? Thanks!