Should I turn off the light in my aquarium overnight?

January 27, 2004 8:19 AM

Should I turn off the light in my aquarium overnight so my fish can "sleep"? Or is that just stupid?

My theory here is that in the ocean, the sun goes down at night so it should be natural for fish to be in the dark a certain amount of time each day. I tried to search on Google, but couldn't find the right combination of search terms.

posted by crawl to Pets & Animals (14 answers total)

I only turn my aquarium light on for a few hours a day (from 7:00 to 11:00 - the light's on a timer) - this is because I have far less algae in the tank if I leave the thing off most of the time. The plants in the tank (java fern) do fine w/ the few hours of overhead lighting in addition to the natural daylight in the room.
posted by drobot at 9:07 AM on January 27, 2004

Actually, I should add that I have a thirty gallon freshwater tank w/ four fish (two african cichlids and two cat fish) - I think that people w/ salt water tanks or w/ a lot of live plants in a room w/ no daylight would have different lighting needs
posted by drobot at 9:08 AM on January 27, 2004

I used to rent a room from a bloke who had a big tank full of cichlids and was quite knowledgeable about them and he was very keen on always turing the light off overnight.
posted by biffa at 9:23 AM on January 27, 2004

Response by poster: This is a very, very rudimentary tank I'm talking about here. Approx 7 gallons, freshwater, plastic plants, etc. I wonder if in this case it just doesn't matter.
posted by crawl at 9:42 AM on January 27, 2004

It seems only polite. In fact, I once read about a system for fish tanks that dims the lights slowly at night, the opposite in the morning, approximating the natural cycle. Seems a bit extreme. But it's not tough to turn off the light at night. Save a little electrical $$, too.
posted by Shane at 9:42 AM on January 27, 2004

This is why I love AskMe.

It certainly can't hurt to turn off the light, as long as you don't have any live plants which rely on it (which, apparently, you don't).
posted by jpoulos at 10:19 AM on January 27, 2004

Like most orgnaisms, Fish follow circadian rhythms. If you doubt this, acclimate your fish tank population to a day/night cycle and try turning the light on for a moment in the middle of the night. They react just as you would. slow moving, groggy actions and trying to get away from the bright light.

(BTW, this is a stressor to their constitutions so I wouldn't advise you make it into a parlor trick to amaze your friends.)
posted by Fupped Duck at 10:58 AM on January 27, 2004

Fish get "stressed" easily, so anything you can do to make them feel more comfortable helps keep them healthy. Turning off the light at night not only won't hurt, it helps... leaving the lights on 24/7 is likely to eventually cause an algae bloom, if nothing else.

If your bulbs don't pull too much power, just get a cheap (under $5 in the U.S.) appliance timer from your local electrical section of whatever store, and set it to turn the lights on and off for you at the same time every day. Never think about it again, and your fish will thank you.
posted by frallyth at 10:59 AM on January 27, 2004

Yeah, turn the light off at night. It does matter, for the reasons you guessed at above. 24/7 light will stress the fish. In fact, if you have good natural light coming into the room, you might just leave the light off most of the day, too, keeping it on in the afternoon/evening when you're around to look at the fish.
posted by tirade at 11:00 AM on January 27, 2004

leaving the lights on 24/7 is likely to eventually cause an algae bloom, if nothing else.

Remove 'likely' and insert 'definately', and you're right. Leaving the lights on 24/7 is just a sure way to achieve a nice dark green coating on everything.

That, and your fish'll probably will be dead within the month from the stress.

Go get a cheap timer and set it for an 8 hour light cycle, and you'll be good to go.
posted by Doktor at 11:43 AM on January 27, 2004

I agree with above, fish have definate rhythms, and they are sensitive to light, so turning it off at night isn't stupid at all. My two-year-old goldfish (plural) are like clockwork with the times they go to sleep, and when they're hungry. Like tirade suggested, I usually let them have natural light most of the day, and turn their tank light off at a regular time.

As a side question, in the same vein of fish sleeping: My aforementioned black moors have developed definate sleeping places in the tank they go to every night, and definate sleeping "partners." While I suppose this give some sort of evidence for fish friendship or at least habit, I was just wondering if anyone else had noticed similar behavior in their other goldfish? It's gotten so that after I clean the tank I know where I have to put certian rocks they sleep next to, otherwise they seem to get upset. Maybe I'm just a little too enthusiastic about my fish.
posted by nelleish at 12:27 PM on January 27, 2004

nelleish - the plural of fishes that are alive is 'fishes' (sorry) - and I've noticed the same thing w/ my cichlids - not that they have particular partners, but that they like things the way they want them - they'll move stuff around even.
posted by drobot at 12:53 PM on January 27, 2004

You know, I'm not so sure about the 'fish' vs 'fishes' thing after all.
posted by drobot at 12:57 PM on January 27, 2004

I turn off the light every night just so that I can sleep. Never mind the damn goldfish.

It also works as a great little alarm clock -- it's on the timer to turn on just before my alarm clock goes on, and it's just enough of a light to make me up from a deep sleep.

Now I'm just training Cheggers the Wondergoldfish to realize that he will only get to eat when the light is on...
posted by Katemonkey at 2:20 PM on January 27, 2004