Nighttime fish colour fading

[davidcalgary29]

I've recently noticed that my smalltooth whiptail, pentapodus caninus, fades almost entirely to a whiteish colour with random brown splotches at night; I actually thought the fish was dead the first time I saw it. But the fish is fine; it resumes normal colouration within a few seconds of the lights coming on in the morning.

None of my other fish show such dramatic transitions to diurnal conditions, including the matted filefish, which has an interesting camo pattern at night. Does anyone have a reason why it adopts this interesting colouration? It sleeps on the sand -- is it attempting to colour match for camouflage?

 

[TangerineSpeedo]

My lawnmower blenny changes it's color to match the surroundings (in grey tones) all the time. It's probable that your fish is doing the exact same thing.

 

[HankstankXXXL750]

I have several fish that lighten as they sleep. Probably for camouflage. Have several species like Hank, my Thalassoma lutescens(Banana, Lime Green, Sunset Wrasse) changes colors for various reasons.
Ours was Line Green when we got it. I moved it to a different tank and it changed colors. I was afraid I had over stressed it or something. The color change was over night or less. Added two new wrasses, Australian Harlequin Tuskfish and Broomtail Wrasse, and Hank changed colors again.