Does More PAR Necessarily Mean More Growth?

[ReefMadScientist]

Hello,

So lets say our water parameters are solid for SPS and we are only discussing PAR. Would more PAR, lets say 250-350 range, increase growth rather than 150-250?

I am assuming every frag is different but I keep thinking more PAR, may be better as long as bleaching does not occur...

 

[Vpham]

Very good topic. ...Interested to hear from others...

 

[bct15]

I have some experiments in the works that will test this very subject, I have read some articles that suggest corals can get too much.

 

[ReefMadScientist]

I have some experiments in the works that will test this very subject, I have read some articles that suggest corals can get too much.

Nice let us know what you find!

 

[pickupman66]

For some strange reason, I remember reading about light saturation in photosynthesis for corals.

Feature Article: How Much Light?! Analyses of Selected Shallow Water Invertebrates' Light Requirements ? Advanced Aquarist | Aquarist Magazine and Blog

http://www.personal.psu.edu/u0y/nanoreef/papers/Chalker (1981).pdf

 

[ReefMadScientist]

For some strange reason, I remember reading about light saturation in photosynthesis for corals.

Feature Article: How Much Light?! Analyses of Selected Shallow Water Invertebrates' Light Requirements ? Advanced Aquarist | Aquarist Magazine and Blog

http://www.personal.psu.edu/u0y/nanoreef/papers/Chalker (1981).pdf

Neat article! The conclusion of their test is that the thought of SPS corals needing intense lighting is not as cut and dry as we all think. SPS coral can adapt to low light intensities as they often do in the ocean. Of course, water conditions and what not play a role in the clarity of sunlight, but for our aquariums, I guess more light is not always meaning more growth.

 

[Fishbone]

In that par range for SPS I would say more par equals more growth. Whenever I move down my lights I always have increased alkalinity and calcium demands. I do feel there's a point of diminishing returns when you get past 450

 

[hart24601]

You must consider flow rate when increasing light intensity. High flow helps to offset some of the problems with very intense light - the main factor being damaging heat in the tissue. You can easily start to inhibit growth with that PAR increase without more flow. There are a few articles about light flow and heat but I don't have the time to dig them up right now.

 

[Big E]

There are a number of variables involved and you can't look at just par alone in reference to growth----

Species--- The type of Sps has a definite bearing how much par it thrives under

Static source--because the light never moves like the sun you don't need anywhere near the intensity that the sun puts out. You also have to be very aware of covering the coral in an envelope of light and not a tight beam.

Time-- The number of hours per day you run the lights have a bearing..........as mentioned above because the light source is static time is a factor.

Color-- Intensity plays a role in the colors

I try to limit the variables and focus on each specie's needs..............

----My par levels are consistent across the whole footprint of the tank........for example at 5" from the bottom the par is 300.
---- I run my lights full on and full off. I don't ramp up or down. If I was going to do any of that, I'd limit it to an hour at most on both ends.
----Through trial and error 8 hours works best for me.
---- From past history some corals are known as par hogs........for example Millis, whereas a Red Dragon needs much less par.

From my experience 200-450 will grow and color any acros, so it's just a matter of putting the particular species at the right level.

 

[Fishbone]

There are a million factors that play into growth, but in general, assuming you have a setup geared towards SPS most SPS will grow quicker increasing PAR from 150-250 to 250-350. That is still on the lower end in my opinion.You'll still need to ramp up the par slowly. I've also found the sweet spot being from about 250-450 with T5s. The amount of time the lights are on will also be a major factor in growth and color.

Lighting type makes a difference too. T5's light the corals very evenly and you can get away with lower PAR level because the corals are getting light from all angles. When I ran halides in the past I found they needed a bit more PAR to reach optimal growth/color because the light is more directional and parts of the coral gets shaded. I don't believe they get hit with as much overall light with MH. You can kind of tell this by the growth patterns and colors you see with a T5 (bushy & evenly colored) vs Halide (vertical & colored more at the top).

 

[jservedio]

Corals can only utilize so much light and the instantaneous PAR numbers themselves matter much less than the Daily Lighting Integral (total PAR throughout total lighting period). The amount of light they can utilize is dependent on the species of coral, the density of the zooxanthella, the spectrum of lighting, and the available nutrients in the water that the coral can access. They can only continue to utilize the available light if the required nutrients are there and when they become photosaturated, additional light will do nothing else.

If your current lighting isn't attaining photosaturation for the coral, than increasing PAR or photoperiod (within limits) will increase growth. However, if you are already photosaturating your corals, more lighting will do nothing at all for growth.