How long to keep the lights on?

[rbraunberger]

Hello all,

How long do you keep your LEDs on? I am running a single Radion Pro30 at 45% for 4 hours, but have the lights on anywhere from 5-15% for about another 6 hours (10 total). Is that to much?!

 

[Mfreddy]

taking into account sunrise and sunset (30 minutes each) I have my lights on for 13 hours total daily. I have 2 Kessil AP700s and run max 40% during the day, 7 hours at that intensity. I have a FOWLR tank.

 

[mcarroll]

12 hours a day, including sunrise and sunset is correct for the tropics.



That's a fun tool to play with to see what that curve is like in different places and different times of the year. (That site has a bunch of fun tools and charts actually.)
http://www.pveducation.org/pvcdrom/properties-of-sunlight/calculation-of-solar-insolation

 

[Nano sapiens]

Hello all,

How long do you keep your LEDs on? I am running a single Radion Pro30 at 45% for 4 hours, but have the lights on anywhere from 5-15% for about another 6 hours (10 total). Is that to much?!

10 hrs. is what corals on a typical reef would experience in the tropics and is what I use for my small mixed reef. The angle of incidence (sun in relation to water surface) needs to be around 10 - 15 degrees before the shortest, most energetic wavelengths (UV, Violet, Blue) start penetrating the water surface in the morning and same applies in the late afternoon when the sun sets. So around 9-1/2 - 10 hrs of actual sunlight hits the reef in a day.

That being said, corals are quite adaptable and do just fine with 12 hrs. or so. This is what many people tend to use since they know that a day in the tropics at the equator is 12 hrs.

 

[mcarroll]

There's essentially an infinite amount of detail to understanding what happens to light when it passes into water.

Did you know underwater is the most dynamic lighting environment on the planet by orders of magnitude?
http://www.ncbi.nlm.nih.gov/pubmed/21113012 (Full article available!)

I like putting 12 hours of light over the tank since that's what the sun does. It's simplistic, but also realistic.

Honestly, you're not wrong with the 10 hours either...I think mostly it's just important not to go over 12 hours. It won't hurt every tank, but you're definitely not favoring the corals by doing longer-than-natural lighting schedules.

Personally, I relax over most of the details (though I am paying attention!) since I know that the lensing effect from waves, as well as many other factors, weigh heavily on the light the corals actually see and use...even the faint light of sunrise and sunset can be useful when magnified by several orders of magnitude.

Just a footnote: If your lights aren't simulating sunrise and sunset and your lights just turn on in the morning and off at night, then (assuming your lights are correct for your tank) you can get away with around 5 or 6 "peak sun hours" vs needing a whole day. I ran my halide fixture this way, and still run my DIY LED fixture on this schedule.