Rainbow fish

[amyleigh89]

hi, i have two turquoise rainbow fish iv had for two months now that are growing nicely and seem very happy!
iv noticed that of a morning when i turn their lights back on they are a really dark browny colour around their head with a even darker strip down the front of thier head! just wondering if anyone knows why this happens! it gradually goes away over the morning, and they go back to being pretty blue and shiny all over

 

[mfdrookie516]

My male turqoise dose that, but the female I have doesn't. I'd say you probably have two males. The reason they do that is when they sleep, they lose much of their color. Typical fish will turn almost ghostly white, but rainbows for some reason seem to darken up a bit.