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

[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.