29 Gallon Tank Should I use a 24 hour sun to moon light?


Hi all. I have bought a 24/7 light that mimics times of the day. I usually just have the light on full power, on a timer for 8 hours of the day(12:00-20:00)

I am wondering whether it's healthy for the fish to have the light on 24hr mode, where it mimics the sunrise and sunset then goes to blue light (moon light) at night. I have read varied opinions on this, and I have noticed that when the light blue at night, the fish don't really rest as much as when there is no light. Of course it looks better for me, but i want to do what is right for the fish. I have read that fish don't see the blue light, so to them it's completely dark, but this contradicts what i have noticed in them. So i am worrying they're not really getting proper sleep time.

Interested to know other people's thoughts on this.



Many aquarists who keep saltwater reef tanks do like to follow the 24 hour sunlight/moonlight strategy. It makes sense with fish and corals who come from oceans near the equator where the water is clear. For freshwater fish, it makes far less sense as they come from a variety of situations. Some fish come from clear waters and some come from very dark or murky waters.


My two tanks the fish did not seem to mind. And I loved it. Being able to check everyone out while they were in sleep mode was nice.

That said, one of the tanks experienced a tremendous algae bloom which may have been attributed to the long lighting period.

I have since gone to manually turning on and off the lights. I give them three hours of the cloudy setting, then full bright for six to seven hours, then completely off the remainder.

The jury is still out on the algae tank. But I do think the growth has slowed.


Fish see blue light. They have, like so many animals, a photo-regulated circadian rhythm. And "unfortunately", they have no eyelids. So for wellbeing, I would, in general, advocate a light pattern that mimics day and night (complete darkness), including a slow transition, of at least half an hour, between day and night, as their eyes need to adapt, and in general do not adapt as fast, as I recall, as human eyes.

As for algae, I agree, blue light, of course, is where photosynthesis peaks, for plants and algae. Except that for plants it pretty much stop after 8 hours, whereas algae can go on and on.

But the intensity of light also matters; hence ensure 8 hours or light that balances between what your plants require and what you personally prefer, and another 4 hours of dim light (0:30 dusk/ 3:30 dawn), regardless the color to enjoy your tank and because it mimics the day-night pattern. Could be "moonlight"; sounds pretty romantic if you ask me. As long as it is dim.

You could also have a peak in the early afternoon and gradually increase light intensity from 6 hrs prior up to the peak and then let it gradually fade out the next 6 hrs after the peak. I adopt this for my tanks and works well for my low light demanding plants, ferns, crypts and buces.

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