Symptoms of too LITTLE light

[JoeBatt]

We all know the burnt tips on corals are the indicator of too high settings on your lighting, especially with some of the high output LED's available today.

But what are the typical symptoms of too low light?

[jeff240gallon]

Overall poor growth I think for the most part, which obviously means your corals can die, certain algae and bacteria won't grow, etc. Also with some corals like zoas will extend more trying to find that light, sometimes polyps get bigger for the same reason (not a good thing). Lots of corals may not even open up if there's not enough light


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[Ron Reefman]

I think corals are kind of like us. If you go out in the tropical sun and spend too many hours out there without proper protection, you'll get burned, you could even get badly burned in just a few hours. However, if you live above the arctic circle, you can survive for 6 months with virtually no sun at all. I know it's not an exact analogy, but the symptoms are just as hard to notice. Corals do capture food from the water, so lack of light and food from photosynthesis of the zooxanthellae may take weeks or months to become obvious.

[JoeBatt]

Thats the thing Im just trying to figure out, the sweet spot where the light is just right. I don't have my lights high enough to burn but then are they too low for growth. Its a puzzle.


Im using Hydra 52HD and 2xT5 ATI supplements. The Hydra can brown toast at the high settings, It crazy powerful ! Yet you see guys turning them up high and wondering why their corals die. I'm down in the early 30% to low 40%. Generally my tank PAR is around 120 to 350 with LPS in the 120 regions and SPS in the higher regions, the spectrum more aimed to the 420nm range. It does fine, but we always want more.

[ReefWreak]

IMO symptoms of too low of light are tough to separate from symptoms of parameter swings or too much nutrients, i.e. the corals turn brown, or their colors just don't show well.

Now, you also mentioned that too much light causes burnt tips. To my knowledge, burnt tips is indicative of too high of an alkalinity with too low of nutrients. I've seen people (and have personally) burnt coral with too much light, and it just causes the colony to bleach overall and start dieing while being very pale in color, but the tips were impacted just as much as any other part of the coral.

Also, another point of reference, but if you're setting your lights to look bluer ("more aimed to the 420nm range"), it is worth remembering that PAR readings undercount blue light unless you have the new Apogee MQ-500 "Full Spectrum" quantum meter (http://www.apogeeinstruments.com/mq-500-full-spectrum-quantum-meter/). So if you're using anything but that one, your PAR in the white spectrum is being counted heavier than your blue spectrum, so if you're weighing your lights heavier on blue to begin with, and you're going by PAR, you're technically undercounting your primary spectrum.

That being said, a Hydra 52 shouldn't burn corals at 30-40% with proper acclimation, but I guess tank depth (and water clarity technically) matters here as well.

[JoeBatt]

Yes ReefWreck, your right its more a sign of to high a Kh ...bleaching is more what I meant to put. I know what I thought I meant I said that I thought ;)

Water clarity is excellent, SPS in the 350ish regions and LPS in the 120ish regions, and no problems. So your saying that my PAR readings are in effect lower than what the real PAR is?

[ReefWreak]

Yes ReefWreck, your right its more a sign of to high a Kh ...bleaching is more what I meant to put. I know what I thought I meant I said that I thought ;)

Water clarity is excellent, SPS in the 350ish regions and LPS in the 120ish regions, and no problems. So your saying that my PAR readings are in effect lower than what the real PAR is?

If you are using anything but the linked MQ-500, then anything coming in to the meter in the blue wavelengths is being under reported. Normally it doesn't matter much, because if you're comparing to someone else on RC who also isn't using an MQ-500, then whatever. The issue is that you said you like a lot of blue, so the more blue PAR you are generating, the more total PAR you are under-reporting.

MQ-500 vs. the old 100 series (and almost every other PAR meter, which is based on the 100 series):
http://www.apogeeinstruments.com/content/sq-500-page/quantum-sensor-spectral-responses.jpg

[JoeBatt]

Mainly the blue spectrum because thats what the corals like.....

So looking at that in the 420nm spectrum you should multiple by 1.43 to get a more accurate PAR? ....ish

(Though that said the PAR will include the rest of the spectrum emitted and since its not purely that range the factor would be less)

[ReefWreak]

You have the math right, that it's whatever proportion of light hits that spectrum that is under-reported, and that would need a boost of whatever % multiplier, then add that back again to total PAR.

Basically you can just use the numbers anyone else has published as a comparison point, since almost all of the PAR meters read off equally. Just mentally adjust upwards if you tend to run your tank on the bluer side or use more blue LEDs.