# Curious Question: How dark do fish like the tank at night?



## kmacF30

Sorry if this isn't "Advanced" (I always have trouble finding the right sections). However the behavior of my fish does create some interesting speculation about nighttime requirements for fish.

I am a firm believer in keeping the tank lights off during evening hours, because not only does too much light stress some fish, but Algae growth can get out of control. But my question really comes down to: is turning the light in the tank off actually enough? Or do fish prefer total darkness to rest?

I bring this up because I suffer from chronic insomnia, and both my tanks happen to be in the bedroom. What I have observed is when my tank lights are off and my bedside lamp is on (its a traditional 60 watt, which does not give off a huge amount of light), The fish are pretty much just as active as they are during the day. However, if while trying to fall asleep I turn my bedroom light off for 2 hours, when I turn my light back on, I Notice my Blood Parrot lying against the rock and all of my rainbows not only brilliant in color, but they are all in a line, at the very top of the tank swimming towards the filter current in with their fins fully spread. They swim in a very restful way. Everybody seems to slow down much more, something I don't witness with any bedroom light on..

If my room isn't getting completely dark, does that mean that my fish are not in an environment that is suitable enough for them to "rest"?


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## lilnaugrim

I would say so. If you think about the wild, most of the time the night is not lit up in any way until the moon comes along and depending on it's cycle, it can be bright as all heck. Fish have an amazing internal clock and they always know when a full moon comes up in some way or another. But for resting purposes, it sounds like you should probably throw a towel/blanket over the front of the tank or whatever side is closest to the light source for when you are awake at night. So that way you can still be up if you need to be and your fish can rest as they need to.

None of this is truly fact but my opinion and what I have observed (the part about the internal clock is true though ^^)


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## secuono

Yes, a tv light, hall light or a little nightstand light is too much light for them to fully sleep. 
Everything goes off for them to sleep. They don't have eyelids to close out the light and can't hide their heads in their wings like birds, so the light does keep them up.


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## Mikaila31

My tanks run on timers and if interrupted most of my fish do still go to sleep about the time the timer turns the lights off even if the lights stay on. I also have a lot of light.


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## RSVBiffer

Whilst fish sleep it is not as we know it, they have periods of reduced activity in an energy saving mode (with reduced metabolism) and is more akin to a nap. This rest includes floating in mid water, resting against a rock or the bottom, holing up somewhere or even continuing to swim but at a reduced rate to keep water flowing over their gills (many species of shark for example). A fish that has had a disturbed period of rest will catch up when the opportunity arises. The general advice available on this suggests that fish should never be kept in a totally dark environment and that some background light is advisable to avoid stress from lights being suddenly switched on.


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## Roccus

anyone that has been out on the ocean or remote lakes at night knows even with only star light the world is never completely dark... some fish are active at night other not as much....most of us use timers on all our tanks...what you can do is provide a shelter ( my fresh water tanks are heavily planted, my marine tank has numerous live rock caves ) with plants or natural wood "root " systems or even rock caves.. then the choice to sleep or not will be theirs... I provide blue LED "moon" lights to all my tanks so they never become totally dark.. the fish that desire darkness will find a cave or dense weed bed to sleep in...the others will forage into the "night" .. eventually they do become conditioned to the length of day you create..


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## pop

Hello Milaila31:
Your post reads somewhat like Pavlov conditioning. Your fish go to sleep on time what else do they do on time?
*I only run lights when I feed the water critters the rest of the time they are basked in ambient light and at night the tanks are lite by reflected light from a salt lamp. I haven’t considered sleeping or napping water critters.*

pop


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## seove

I run blue led moonlights for several hours after the lights go off. 



kmacF30 said:


> Sorry if this isn't "Advanced" (I always have trouble finding the right sections). However the behavior of my fish does create some interesting speculation about nighttime requirements for fish.
> 
> I am a firm believer in keeping the tank lights off during evening hours, because not only does too much light stress some fish, but Algae growth can get out of control. But my question really comes down to: is turning the light in the tank off actually enough? Or do fish prefer total darkness to rest?
> 
> I bring this up because I suffer from chronic insomnia, and both my tanks happen to be in the bedroom. What I have observed is when my tank lights are off and my bedside lamp is on (its a traditional 60 watt, which does not give off a huge amount of light), The fish are pretty much just as active as they are during the day. However, if while trying to fall asleep I turn my bedroom light off for 2 hours, when I turn my light back on, I Notice my Blood Parrot lying against the rock and all of my rainbows not only brilliant in color, but they are all in a line, at the very top of the tank swimming towards the filter current in with their fins fully spread. They swim in a very restful way. Everybody seems to slow down much more, something I don't witness with any bedroom light on..
> 
> If my room isn't getting completely dark, does that mean that my fish are not in an environment that is suitable enough for them to "rest"?


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