Lighting duration/frequency

FishFanMan

FishFanMan

AC Members
Jun 13, 2013
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16
Naperville, IL
Hi,

My tank is just a month old and I have some nice swords and anubias which are growing nicely under my 30" LED lights in my 16" high 34 G tank. I'm thinking 8 hours is enough for these plants and hopefully not enough to cause algae to establish in my tank.

Is there harm (not good for plant health) if I turn my lights on for 4 hours, then off for 4, then on for 4, then off for 12 hours?
To be exact my timers are set for moon lighting 6am to 7am, bright lights 7am to 11am, no lights 11am to 3pm, bright lights 3pm to 7pm, moon lighting 7pm to 11pm, no lights 11pm to 6am.

Does darkness in between the total 8 hours of "sunshine" cause any sort of issues with plant health?

Thanks.
 
The only reason I'd avoid doing that is it doesn't mimic a normal light cycle. Not sure if that effects the photosynthesis process on the plants though.

Why the 4hr break in the middle? LEDs don't consume much juice, nor should they heat the tank?
 
There is actually some evidence that supports breaking up the photo-period allows plants to more efficiently use the light. The theory is that it allows the plant to balance out the C02 levels (internal to external). 4 hours is a bit long however. Plants also have a lot of hormonal responses to light. You can trigger plants to bloom etc... with different daylengths.

Since most plants in the hobby are from the tropics or sub-tropics, I've always had good luck in my low-tech plants on a 12 hour time schedule. If you pumping high light and CO2 you'll want to scale that down.
 
The only reason I'm doing this is to maximize the time we see the tank with the lights on.
After lunch, we don't pay much attention to the tank so there's no benefit to us for the lights to be on. When we are back home, we'd like to see the tank lit up and enjoy that. So if we had the lights on from 7am to 7pm, that might be too much light and may lead to algae bloom. That's why I'm doing 4hrs in the morning then 4 hours in the afternoon to early evening.

If algae doesn't grow in my tank, I may increase gradually to 10 or all the way to 12hrs. I created a high flow tank to minimize algae and I use a UV light 24/7 to help keep algae from multiplying also.

As a side point about heat from my LED, I noticed my light doesn't give off much heat at all. But my UV light gives off significant amount of heat that is transferred to the water. So much so that I don't use my regular heater now. The UV light maintains my 34 G to a very steady 79 degrees. I set my heater to 76 in case UV light fails and I don't notice it. I have my AC set to 76.

Anyways, thanks for the posts.
 
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