These LED's just aren't cutting it. Or - are they?

[waynemah]

Originally Posted by Slyguy00

Was that at 100%?

Those had 80 degree frosted optics and were run at 80% on the white and 100% on the blue. Having no optics will make our heights different, but raising the fixture itself is a tool to improve coverage and lower the brightness at the same time. If your coverage is good, drop the brightness.

[Slyguy00]

Is there an average height people run their lights above the sand bed? I just hung my maxspect razor yesterday and am not sure if I should keep it at the same height as the legs (like 8") or move it up more.

[The Guy]

Originally Posted by Slyguy00

Is there an average height people run their lights above the sand bed? I just hung my maxspect razor yesterday and am not sure if I should keep it at the same height as the legs (like 8") or move it up more.

I have my AI's 12" above the water line I ramp up to max. on blues & royal blues @ 80% with whites @ 60% starting 3 pm to 4:30 pm what I call mid day sun. Then ramp down from there. Had to play with them to get to a sunrise to sunset that gave me the best over all light for the corals, I probably could treak more but this seems to work for me so far.

[Ron99]

I think there are so many misconceptions around LEDs even after several years of use and a more mainstream acceptance. You could happily grow corals under nothing but white LEDs. The coral would get enough light for photosynthesis and grow but the colours would not look pleasing to our eyes. You could also probably grow corals under nothing but blue LEDs but, again, the colour would likely not be what we want for our own enjoyment.

All the other colours of LEDs being added to fixtures; green, red, violet; are not necessary for growth or coral health but are useful to fine tune the "look" of the corals for us.

As for the topic of this thread, bleaching does indicate too much light. Blue is high in PAR in the spectrum that corals utilize so turning them down or raising your fixture will help. And you need to give the corals time to acclimate to the new light intensity. They won't change overnight.

IME, it's better to start LEDs higher or at lower power and have your corals start to brown a bit, then turn them up or lower them than it is to shock them with too much light and bleach and potentially kill them.

[Jakegr]

Originally Posted by Ron99

As for the topic of this thread, bleaching does indicate too much light. Blue is high in PAR in the spectrum that corals utilize so turning them down or raising your fixture will help. And you need to give the corals time to acclimate to the new light intensity. They won't change overnight. .

Just a note - blue light is not higher in PAR than red light. PAR is measured as umol photons 400-700 nm / m^2 / s. The PAR from 20 photons of blue light is equal to 20 photons of red light. I think you mean blue photons contain more energy than red photons, which is completely true. This is a bit of weakness when relying on PAR as your sole indication of light quality... it values all photons between 400-700 nm equally.

Also, re: growing photosynthetic organisms under monochromatic light - there are usually a lot of problems with that as blue light, red light, and far red light play many non-photosynthetic physiological roles. You are completely right about growing corals under white LEDs only as that is not monochromatic light. Growing them under only blue or only red probably is not a good idea for the health of the coral.

Also, the PAR meters used by hobbyists miss blue photons and tend to underestimate PAR in fixtures with a lot of blue light.

I think a lot of misconceptions about LED lighting are due to hobbyists having misconceptions about the nature of light and its measurement.

[Ron99]

I doubt that those really cheap generic fixtures are using meanwell drivers or decent LEDs. You just can't get them at that price point. Some other slightly more expensive fixtures may be using Bridgelux LEDs (which are pretty good) and possibly Meanwell drivers. Some may even be using Cree emitters. But there are also different levels within Cree LEDs for example because LED manufacturers bin their LEDs according to output and colour so the higher bins will have higher output and colours closer to their ideal rating. Higher bins are more expensive. So cheaper fixtures are likely using lower bins of LEDs than the more expensive ones.

Can you get good results with less expensive fixtures? Absolutely. But you might not have longevity, maximal output if you need it for a deeper tank, or just general build quality. They have to cut some corners if they are keeping prices down, especially with the really cheap fixtures.

Jakegr: you are correct and I suppose I didn't explain myself fully or clearly. What I meant to say was that blue LEDs emit close to one of the chlorophyll absorbance peaks (as well as the absorbance peak of carotenoids which may or may not be important in corals) so they are providing lots of PAR to the corals even though they may look dim to our eye. So having them run at high output could be bleaching out your corals even though they may seem dim to you.

And it is well known that PAR meters underestimate the PAR at the blue end of the spectrum as most were designed to be used for measuring light for terrestrial applications rather than under water.

[jason604]

I'm happy with my "cheap" LEDs. Thaotronic dimmable led version seems to have tons of great review.cant say the same for there other fixtures. Boy it must feel dumb paying up to 10x as much as I did and get about same results =). Being on student budget these were the best choice for me. I have my blues at 60% and whites at 50%. Should I crank it to full blast?