does too much light affect coral growth?

[Rich D]

I know that too much light will cause corals to lose color, but does it change the rate of growth?

[DIONE@AQUATICA]

From everything I have read they say that in can effect the coral growth. I have heard many reefers and just reading what the tank of the month guys say about light periods. Consistency as far as when you turn on and off lighting has to do with it to. Your coral will probably still grow but might not have the same success as other might with the same setup. Good luck with your tank.

[jbird69]

i think the danger with "too much" light is for a coral that isnt used to it. Acclimating corals to lots of light is super important. Too much light all of a sudden can kill coral.

Its also worth mentioning that there are differnt light requirements for different corals. Mushrooms don t like as much light as acros. most soft corals have much lower light requirements than most sps...and most lps fall somewhere in between.
But too much light will not make corals lose color...too much light too quickly (lack of acclimation) certainly can.

Also kelvin temperature has a great deal to do with how much color and how quickly your corals grow.

[MileHighFish]

I dont think any of us is putting out the energy of the mid day sun in the tropics. . I agree with jbird acclimation is the key and some corals are from a lower area of the ocean and dont need super bright light.

[tmz]

Corals exposed to too much light too quickly may expell zooxanthelae,bleach/loose color. The light stimulates unhelathy levels of zooxanthelae and photsynthesis which produces too much sugar and oxygen for the coral. It responds by expelling it's symbiotic algae and or closing up. It may become photoinhibited and not open fully for a long period of time and may die as a result. I don't think it will grow very much with these stresses in action. Different species of corals have different lighting needs which should be studied and taken into account when making a placement. Even those requiring high light should be moved up toward the light over a week or so, unless they are moved from one high light tank to another,obviously.

[Rich D]

I have a relatively new tank with only a couple corals, and have just established a new sump in the basement. Because of our new england weather the greater surface area in the basement caused an immense tempurature drop when the lights were off. To compensate for the drop, we increased the photo period untill we could get another heater (we are now running 3 250 watt heaters and it seems to keep the temp level). All of the lps are looking great but the sps seem to have bleached although the polyps are still fully extended. The are new corals so it could be an acclimation problem since we do use MH 10000k bulbs. We are now starting to lower the photo period to see how the coloration reacts...

[tmz]

Hard to sort out wether your sps bleached due to temperature or lighting. Generally the length of the photo period for metal halides within reason wouldn't hurt them in my experience since they can close up for part of that time.

[Rich D]

The polyps are doing fine, they are usually fully extended and have pretty good color, its the actually body of the corals thats losing color. I want to say its a lighting problem because part of it that is shaded has more color than the parts in direct light

[jbird69]

Do you have any sps that arent bleached? or are all of them like that. Also, have you tested your dkh, mag and calc. sps are a bit more temperamental to these properties than lps.

Also 10000k bulbs are more in the yellow spectrum and wiil encourage faster growth at the expense of color. You will never get the vibrant colors at 10k as you will at 14 and especially 20k. tho your growth wont be as rapid. Do you have actinic suppliment? this is a good way to get growth and color.

[Rich D]

Well because its a pretty new tank, the only sps are either recovering from a cyano bloom, or are brand new. There is actinic supplementation. Do you mean my growth will be more rapid?

"tho your growth wont be as rapid"

[IslandCrow]

All corals have a point at which too much light will negatively impact them. This is aside from acclimation issues, and is known as photoinhibition. According to Wikipedia (yeah, I know it's not exactly a scientific journal worthy reference, but it's convenient):

Photoinhibition is a reduction in a plant's (or other photosynthetic organism's) capacity for photosynthesis caused by exposure to strong light (above the saturation point). Photoinhibition is not caused by high light per se, but rather absorption of too much light energy compared with the photosynthetic capacity, i.e. any excess energy that the photosystem cannot handle is damaging.

This point of photoinhibition is going to be different for each coral. Although, we generally don't have lighting systems that get anywhere close to the sun, also remember that some of these corals live 10, 20 meters or more under the surface. In other words, you're probably don't have to worry about too much lighting with a coral that grows near the surface, like Acropora, but it could certainly be an issue for some of the deeper water corals.

[jbird69]

Sorry, I have a bad habit with run-on sentences. your growth wont be as rapid with 20k as it will with 10k. Tho with your 10k and some actinic t5, you should experience the growth of 10k lighting while the t5 will bring out some color in your corals.
There are a few factors to corals losing color. EVERYTHING in this hobby falls back on patience. it is the foundation of keeping a successful reef. With patient acclimation, over time, if you have excellent water, your corals will come into their own.

In your case, I would either shorten your photoperiod and gradually, over a couple weeks, get it back to its regular schedule. Or do the screen method to filter light for a week or two. It sounds like your corals might have light shock from sudden, extreme increase in PAR. Tho when I have experienced this I am usually seeing minimum polyp extension...which is why I asked about your dkh...etc.

[Rich D]

im going to go test the harndess right now, the calcium is around 350-400, is this too low? I didnt want to play with it too much because it stays at a pretty consistant level.

[Rich D]

never mind, my test kits seem to have run away. ill have to ask my dad where he put them later

[Peter Eichler]

Originally posted by bubbles129129
The polyps are doing fine, they are usually fully extended and have pretty good color, its the actually body of the corals thats losing color. I want to say its a lighting problem because part of it that is shaded has more color than the parts in direct light

Your corals are not bleaching, they're lightening. I suppose it could lead to them being bleached but it's unlikely. The term bleaching, when it comes to corals at least, is usually a quicker phenomenon and leaves the coral void of zooxanthellae. I'd suggest lessening the exposure for the corals in question and perhaps cutting back your photoperiod by a couple hours. Sometimes feeding more can help as well.

[Peter Eichler]

Originally posted by IslandCrow

This point of photoinhibition is going to be different for each coral. Although, we generally don't have lighting systems that get anywhere close to the sun, also remember that some of these corals live 10, 20 meters or more under the surface. In other words, you're probably don't have to worry about too much lighting with a coral that grows near the surface, like Acropora, but it could certainly be an issue for some of the deeper water corals.

Very few of the corals we keep were probably collected at or near the surface of a coral reef. 10 meters is probably a very common level for collecting. Also, Acropora is about the most diverse group of corals out there and occur in a very wide range of lighting conditions. You probably know this, but just pointing it out again to hopefully dispell the common belief in this hobby that all SPS coral must be blasted with light.

Once upon a time in this hobby is was common to say that our lighting systems can't compare to the sun. Well, I think we were wrong. With todays lighting I'm sure there are many reef aquariums out there subjecting their corals to light levels far higher than what they would often see on a natural reef. Especially when you consider many if not most of our corals aren't coming from or originating from the upper limits of the reef.

[jbird69]

Especially when you consider many if not most of our corals aren't coming from or originating from the upper limits of the reef.

This is a great point. Many of the corals we buy/trade have NEVER seen anything but artificial light.