Re: [RML] Fish Sleep

Adrian Tappin (atappin at
Wed, 15 Sep 1999 05:56:47 +1000

At 03:05 14/09/99 +1000, Matthew wrote:
>Dear RML,
>Is there any adverse effect of fish never experiencing the dark?
>Do fish need sleep?
>If so can they get it when there is always a light on?
>A new security light system has been installed in my office which keeps a
>small amount of light on some of my work fish tanks all night. Should I be

Rainbowfishes are certainly affected by external environmental factors which
in turn will trigger internal biological functions. One of the external
environmental factors that have been shown to play a significant role in
their life cycle is the photoperiod.

I don't really know if continuous light will have a detrimental effect on
them long term, but it does increase their metabolism and their spawning
behaviour. I guess if the light is not a bright light then it shouldn't
bother them too much as I would imagine that the natural nighttime is not
completely dark (moonlight etc).

And yes, they do sleep and if you sneak up on them in the dark and disturb
them they go into a mad panic. Also they have a different night-time
colouration as well.


Adrian R. Tappin
Brisbane, Australia.
"Home of the Rainbowfish"