Lighting: intensity vs duration

[mpderksen]

I'm running an Led kit from Rapid on a Reef Reeper. I have a mixed population with a few SPS, a bunch of softies and a BTA. I would like a longer photo period so I can enjoy the tank longer than the 8 hours it is currently set at. But I'm also struggling (but winning) a GHA battle. Could I reduce the intensity from 60% to 40% and add a few hours? I don't want the SPS specifically to suffer.
I assume in a natural environment they get 10-12 hours.

 

[alton]

What are your PAR levels? You are wanting to reduce the amount of light from 60 to 40% of what? If you want to control hair algae add a reactor with GFO. I don't mean to sound bad, but with any light you have to know how much light it is putting out?

 

[oscarinw]

Hair algae, from what I can understand doesn't need high intensity to thrive, so reducing the light intensity will not 'bother' the GHA. However, extending the photoperiod will definitely aid its growth. I would recommend to start an hour earlier and end an hour later with only blue light if you can control color channels. That will give you extra time and might not have an impact on GHA growth... maybe.
give it a try and see how it goes. Extra rock, extra sand, no bio balls, socks, carbon dosing and water changes with high quality water seems to be the formula for GHA control so I'd suggest using those as well.
Good luck

 

[LobsterOfJustice]

If anything, I would do the opposite. Corals, even SPS, only need 4-6 hours of intense light daily. If you are trying to choke out algae you might even get away with 3-4 hours for several weeks. Anything past that is just viewing light that is growing algae.

 

[LobsterOfJustice]

Once you get the algae under control, I would run the light on a low level for viewing purposes only for the rest of your photoperiod. I don't have LEDs but I do this with my light setup - I run two VHO tubes for 12 hours a day and run my MH for 6 hours. You are right about there naturally being 12 hours of daylight, but not nearly all of this is peak sunlight time. There are really only a few hours a day when the sun is overhead that the corals get high intensity light - the rest of the day is just ambient.

 

[snorvich]

Once you get the algae under control, I would run the light on a low level for viewing purposes only for the rest of your photoperiod. I don't have LEDs but I do this with my light setup - I run two VHO tubes for 12 hours a day and run my MH for 6 hours. You are right about there naturally being 12 hours of daylight, but not nearly all of this is peak sunlight time. There are really only a few hours a day when the sun is overhead that the corals get high intensity light - the rest of the day is just ambient.

Actually with controllable led's you can do that too. I simulate a day with sunrise, noon sun, and then diminishing to sunset (when the fish mate).