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Where Is Your PAR?

George Monnat Jr

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Recently some of my stuff has looked unhappy. Specifically, a Green Mushroom, a Lavender Ricordea and the little Electric Blue Digi that I found. I recently moved the digi up onto a LR, but I haven't moved the mushroom or ricordea in weeks. Of course, one of the Green Mushrooms has been shriveled and bleached for weeks, as has the ricordea. I assumed all were reacting badly to increased light, so yesterday I pulled out my PAR meter, changed the batteries (which were just about dead) and mapped my PAR levels.

I found that the Green Mushrooms had been moved under a light and were experiencing PAR of 106. My other mushrooms, which all look happy, are in PAR levels of 26-61. Except for a Rainbow Mushroom that is doing ok at a high PAR of 139. I measured to the left of the Green Mushrooms where I think they were last year (month or two ago), and it read PAR 64.

The Lavender Ricordea has been around PAR 130. That's a bit high, but I have Orange and Purple Ricordea there that seem happy.

The Electric Blue Digi was now at PAR 136. When it was on the substrate, it was less than PAR 130 (sensor is too big to get down to the same spot). That's not much of a difference, but it hasn't extended its polyps since I moved it.

Pretty much everything else fell within the PAR ranges that I expected, or at least seemed happy where they are. I have two sets of Pulsing Xenia. The set in PAR 160 are happy, while the set in PAR 60 are slowly roaming (unfortunately in the wrong direction, they think up equals higher PAR but no lights there). I've been using this conference slide that was posted in an RC thread by an ARC member as my guide:


Here are some example PAR readings for my critters, all of which look happy:

Green Polyp Birdsnest (Seriatopora guttatus): 191 [about right according to chart]

Blue Tenuis (Acropora tenuis): 76 [definitely low according to chart but best polyp extension I've seen in a year]

left Branching Frogspawn Coral (Euphyllia paradivisa): 84 [low according to chart but looks great]

right Branching Frogspawn Coral (Euphyllia paradivisa): 149 [correct according to chart but doesn't look as good as other]

Metallic Orange Mushrooms (Discosoma sp.): 26 [very low according to chart but growing to about 2" and reproducing regularly!]

KO Nightmare Cousins Palythoas (Palythoa spp): 64 [about right according to chart]

Candy Cane Coral (Caulastrea furcata): 163 [about right according to chart]

Yellow Fiji Leather Coral (Sarcophyton elegans): 83 [little low according to chart but growing gangbusters with great polyp extension; maybe trying to reach more light?]

I finally got a copy of The Reef Aquarium, Vol. 3: Science, Art, and Technology by Delbeek and Sprung (only volume I have so far). On page 448, they show a chart of PAR in a 15' tank with levels from 3692 µmol/m2/s at 1/2" down to 295 µmol/m2/s at 15'. That surprised me, since, "On a blue sky sunny day, the sun produces about 2000 µmol/m2/s of light as measured with a PAR meter…" [from here]. With PAR values almost twice the sun, how was anything alive in that tank? When I first got my PAR meter, I went outside and read almost 2000 pointed at the sun.

The Delbeek and Sprung vol. 3 on page 449 states, "The greatest variety of coral growth occurs at depths between 10-15 m (33 and 50 ft.) where light intensities are lower then 20,000 Lux (Dustan, 1982) or 300 µmol/m2/s (Harker, 1999b)." That < 300 PAR jives with the chart above and what I thought.

I did a new search and found the CORALIFE Aqualight LED Interactive PAR Map. I made an extra tab on my spreadsheet that shows these values from that interactive site:


The CORALIFE chart has much higher values than the slide and my values. My LEDs are being run on an 85% duty cycle, so I could bump all of the values by an extra 15%, but everything seems happy or like there's too much light.

After all that, I get to my question. If you've used a PAR meter, what values are your invertebrates under and are they happy?

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I'm sure other people will ask this.

But.... I don't know my par values, but if you want to swing by with your meter we can find out!

I'm actually also tempted to see what my current readings are, and my readings next week. I plan on upgrading my ballast to a newer electronic one. I wonder how much more light it will put out.

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Here are a few of mine under two different types of light (both were taken with the bulbs a few weeks old)

Coral Phoenix 14K 250 watt MH XM 10K 250 watt MH

RBTA 155 175

Candy Cane 117 35 (I had to move it as it was stung by the RBTA and tested the lights to see what it was where I put it)

Appleberry monti 156 160

Bubble Coral 45 80

Acans 150 250

Hammer 115 200

Zoas 199 300

Superman monti 184 140 (I had to move it)

What I have found is:

par changes quickly from one spot to another-even a inch or so can make a big difference

Not all bulbs are the same-one of my XM 10k bulbs puts out only half as much par as the other

I plan on switching to LED's over the next year as I am tired of trying different MH bulbs and getting different amounts of par and also having to acclimate every year.


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The bicolor birdsnest I posted here: http://www.austinreefclub.com/topic/24054-the-difference-a-12-inch-makes/ is getting 350 on the left side, 200 on the right side and 75 on the shelf by the base of the colony where M. digitata is growing quite well although it has very little purple.

And in this tank the PAR readings are:


The Green slimmer is pretty much the same color through out the change in PAR. The Frogspawn, Euphilia divisa, in the lower right corner (brown with green "eggs" variant) is certainly getting 200 PAR if not more

The whole chapter on lighting by Delbeek and Sprung is an excellent starting point for aquarists to understand better the role of lighting on reefs. I personally am leary of using rules of thump or charts that strike me as far too generic and would point out Delbeek and Sprung do not use the scientificly invalid terms "SPS" or "LPS". We are dealing with thousands and thousands of different species and variants (some variants arguably domesticated) and some are quite adaptable while others are not. I myself have kept frogspawn, Euphilia divisa (green with tan "eggs" variant), in just 10 PAR for years with very good polyp expansion (obviously), albeit there was little growth and you can see in the picture variants can acclimate and do well with 200 or more. (For another example Porites porites and P. branneri while closely related and both having similar purple variants demonstrate very different tolerences to light intensity, P. porites will grow from the 3 feet to 160 feet deep while P. branneri will only grow between 15 and 30 feet.) Additionally color is often influenced by intensity and/or spectrum so research is critical in matching lighting and speciman to each other for optimum results. Research is also demonstrating the conditions a coral was grown under influences it's environmental requirements, consequently different specimans grown in different environments will bleach under different conditions ( http://www.mendeley.com/research/experience-shapes-susceptibility-reef-coral-bleaching-3/ )

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Thank you troypt and Timfish for your numbers. troypt's numbers are on par with mine (best word, no pun intended), and Timfish's are definitely higher. My "big" LED squares are in the front to push photons through 19" of water while the strips in back only need to go through a few inches before hitting LR. That means I have uniformly low/medium PAR of 100-200. According to the 1st chart, I was happy with that as I have few SPS and mostly corallimorphs. The 2nd chart shows that my levels are too low. I know those are generalities, but I need initial targets. I'd like a good starting point instead of losing livestock through extensive and random trial-and-error.

I've wanted more light for awhile but can't afford it right now. I just want to make my stuff happy enough to where nothing dies until I can get more. As I said, the stuff that looks unhappy (except the migrating Xenia) looks like they have too much light. Has anyone seen coral keep their polyps in due to low light?

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Tim (timfish) came by today and did some PAR readings on my new LED setup...


took PAR readings of the t-5s that I had in my tank back in December...

The results were about 120 in the center on the bottom of the tank with

10 48" 54w t-5s and around 400 at the water level. That was with

540Watts of t-5 lighting...

With 200w of LED lighting I am getting the following:

Blues only:

LEDs are about 10" from water surface

100 at surface

55 8" under

45 10" under

40 14" under

40 bottom of tank 24" under...

Whites only:

170 at surface

70 10" under

50 12" under

50 bottom 24" under

ALL lights at 100%

300 at surface

120 10" under

110 14" under

100 bottom 24"under

Take about 10 points off of each number on the edges of the tank otherwise the lighting is very even.

Thanks Tim!

Cool, thank you. Is your lighting still the same, and is everything happy?

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Actually I think readings of the bicolor birdsnest, http://www.austinreefclub.com/topic/24054-the-difference-a-12-inch-makes/ shows so both the birsdnest and Monitpora digitata growing well under 75 PAR. There is better color with higher PAR readings and in fact I can get a very nice lavender coloration from the birdsnest with 600 PAR as well as a almost solid growth form much more reminiscent of a tabling type coral but the base of the colony is doing well at much lower readings. After reading Dana Riddles articles on coral coloration (start here http://www.advancedaquarist.com/2009/1/aafeature1 and here http://www.advancedaquarist.com/2006/9/aafeature ) it seems clear to me lighting for corals is far more complex than looking at just photosynthesis. Many of the fluorescing and chromoprotiens are dealing with light, either absorbing in the case of chromoprotiens or absorbing and reemitting with the fourescing protiens, wavelengths in the UV range and green yellow and orange spectrums. The question is why?

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