low PAR acro progression (1 year)

[acro-ed]

After all these years I was finally able to get some actual PAR readings on my tank. The results were quite low.

I am running 8x 80w T5 (ATI sunpower) and 3x Radion Pro gen.2. The readings were taken with my old bulbs which are about to be replaced and the Radions at approximately 30%. They do ramp up higher for part of the day, but the coral below is all the way on the bottom glass at 27" depth.

The PAR on this coral is ~160 for most of the day.

It will likely jump up a little for a few hours during the brightest part of the schedule, and likely a little more when the fresh bulbs go in, but I believe on average this coral gets 150-200.

I wanted to share because I feel that I am getting considerable growth at a PAR level well below what is promoted in many SPS PAR discussions.

This isn't a discussion on the "value" of higher PAR, because I definitely have some acros that "need" more.

The point is that you may need less than you think for many acros and still have excellent color AND growth.

Thoughts? Comments?

Thanks guys!
Ed


(Pics Jan 2018, July 2018, Jan 2019) - note: encrustation was popped off and moved to my new tank also on the bottom glass with substantially similar lighting on April 8th, 2018.

 

[BestMomEver]

Wow! Definitely worth discussing. Like you said, some SPS probably need more light. Perhaps some of them come from deeper water. Beautiful coral, BTW!

 

[drawman]

Well with that lighting my guess is you're getting a good solid distribution with very little shadowing (depending on tank dimensions of course). So even though the PAR is lower it's probably consistent light throughout.

 

[tankstudy]

I think this maybe the case for some acros/sps corals. I'm mainly a zoa/paly/softies keeper but I have kept some sticks/sps type corals over the years and I have seen good growth and color on them. Most of my stuff was growing under 33-76 par using a Radion XR30 Gen 3 Pro.

I recall seeing an article which had a list of sps that would possibly grow under lower lighting, one of them was the strawberry shortcake. Next time I'm out and about buying coral, I'll have to remember to get a piece and test it out.

 

[acro-ed]

This is a 300DD (6' x 3' x 27").

I agree that the even coverage is likely an important factor here.

Thanks!
Ed

 

[biophilia]

A lot of the "required" PAR numbers for stony corals thrown around in the hobby don't make much sense to me. A surprising number of species we keep reach photoinhibition in the low 200s. 150-220 PAR is probably adequate for good growth and color in most cases as the zooxanthellae can pretty easily adapt by increasing chlorophyll a density...

Of course that fact doesn't help sell bigger, brighter, and more expensive lights!

 

[jda]

Quality matters are much as quantity and you should have all the quality that you need with the 8x T5s. Also, total time is a factor... 4 hours at 160 might not get it done, but 10 hours at 160 could.

Also, make sure that you have applied all the necessary factors to the PAR meter - some need adjustment by 1.32, 1.06, etc and some need none. When dealing with absolute numbers, it really can matter.

 

[acro-ed]

This was taken with the older Apogee MQ-200. Is there a correction factor for this model? I admit I'm ignorant to this aspect of lighting.

I am simplifying it a bit, but the light cycle is 12 hours: 8 hours of higher intensity (30-80% radion and 8 T5) and 4 hours of low intensity as dawn/dusk (0-30% radion and 2 T5).

 

[jda]

I am going off of memory, but the IIRC the mq-200 needs 1.32 applied to all measurements - so your 160 PPFD will be more like 211 PPFD. It might even need a 1.06 applied on top of that... which gets it closer to 225.

For handheld, mq-210 and mq-510 have them applied already and are ready to use out of the box with no correction factors... all others need some sort of something.

Dana has written about total-time and output... so 8 hours of 400 PPFD (3200 total) is the same as 10 hours of 320 PPFD as long as you stay in the range of minimum-to-get-photosynthesis-going and photo inhibition and have a reasonable period of dark time. (1 hour of 3200 is not going to work and neither is 20 hours of 160)

 

[OriginalUserName]

Nutrient content in the water must also have an impact right? More available for direct uptake and/or via polyps means less demand on zoxanthele.

 

[jda]

Zoox are the only thing capable of giving the coral energy... which must come from light. Some coral can catch food with carbon in it, but it is not likely that this happens with Acropora with what we have to feed them - there is no evidence that they can catch it in high enough numbers, nor if the gained energy was worth the net expense. If you are talking about the building blocks (nitrate and phosphate), they are necessary build new tissue and to repair (to a degree), but they cannot give coral energy like sugars from the zoox do - with N and P, once you have a surplus (even at very low levels), then more does not really do anything.

Even though it is possible that some corals can catch some food that they can get value out of, without much of any proof (and even some that says otherwise), it is best to just meet all of their needs with light and then if they do catch some food, then that is a bonus.

 

[OriginalUserName]

Zoox are the only thing capable of giving the coral energy... which must come from light. Some coral can catch food with carbon in it, but it is not likely that this happens with Acropora with what we have to feed them - there is no evidence that they can catch it in high enough numbers, nor if the gained energy was worth the net expense. If you are talking about the building blocks (nitrate and phosphate), they are necessary build new tissue and to repair (to a degree), but they cannot give coral energy like sugars from the zoox do - with N and P, once you have a surplus (even at very low levels), then more does not really do anything.

Even though it is possible that some corals can catch some food that they can get value out of, without much of any proof (and even some that says otherwise), it is best to just meet all of their needs with light and then if they do catch some food, then that is a bonus.

Yes I was thinking along the lines of micro nutrients like nitrates etc. Thanks, I'm still trying to wrap my head around the impact of "dirty" water.

 

[acro-ed]

Just for the sake of discussion if you're looking to evaluate photo intensity/duration vs. nutrient levels, I'm at:

NO3 = 25 ppm

PO4 = 0.02 ppm

 

[Reefahholic]

Stunning Ed! For a long time I’ve thought we overestimated PAR. For some corals it’s definitely true, but I’ve seen others now blow up much faster in higher PAR like 450-480, but some just flat don’t like it even with all the traces dialed in.